DEV Community: Brayan Vasquez

Ruby on Rails Cron Jobs Using Whenever

Brayan Vasquez — Tue, 17 Nov 2020 00:52:03 +0000

Hi Everyone!. In this post, I want to share with you a little guide that will show you how to use cron jobs in a Ruby on Rails application.

Requirements

Ruby (I use ruby 2.7.1p83)
Ruby on Rails (I use Rails 6.0.3.4)

Note: I advise you to install ruby using a version manager like rvm or rbenv. Also, I recommend the GoRails Tutorial that will guide you throughout the process.

What's a Cron Job?

A cron job is a process that is scheduled to run at a certain time (every minute, day, week, or month). On Unix systems, we can run and manage these types of processes using the cron tool. The info of the process that will run the cron tool is stored in a file called crontab.

Examples of the use of cron jobs are the following:

Generate reports. e.g, a report of daily payments from an e-commerce application.
Send reminders to users. e.g, send offer reminders from an ecommerce application.
Modify the status of the records. e.g, canceling payments that exceed a time limit to pay.

We can see our cron jobs using the following command

crontab -l

To delete user jobs we can use the following command

crontab -r

And to edit our crontab file, we can use the following command

crontab -e

The structure of a cron job is the following

.--------------- minute (0-59) 
|  .------------ hour (0-23)
|  |  .--------- day of month (1-31)
|  |  |  .------ month (1-12)
|  |  |  |  .--- day of week (0-6) (sunday=0 or 7)  
|  |  |  |  |
*  *  *  *  *  command to execute

An example of how to define a cron job to execute every 5 minutes

*/5 * * * *  /home/user/test.rb

Setup the project

Now that we know what's a cron job, we can start to write code. First, we are going to create our rails project.

rails new whenever_example

Add whenever gem

Whenever is a gem that helps us to define cron jobs in a readable way. So, we will add this gem to our Gemfile.

# Gemfile

# Cron jobs
gem 'whenever', require: false

Install our dependencies

bundle install

Create a rake task

We will use a rake task to run in our cron job. First, create a .rake file.

# Create the rake task
touch lib/tasks/whenever_test.rake

On our task, we will simply print a message.

# lib/tasks/whenever_test.rake
desc 'Whenever rake task test'
task whenever_call: :environment do
  Rails.logger.info "Whenever task"
end

To see the rake tasks of our Rails application, we can use the following command.

# See all tasks
bundle exec rake --tasks

# See our task
bundle exec rake --tasks | grep whenever_call
# rake whenever_call                      # Whenever rake task test

We can execute our task to check that it works.

bundle exec rake whenever_call

In our logs file we should see the message we define.

tail log/development.log
# Whenever task

Define our cron job

First, we have to setup the whenever gem.

bundle exec wheneverize .
# [add] writing `./config/schedule.rb'
# [done] wheneverized!

This will create the config/schedule.rb where we will define our cron jobs. We will create a simple task that will be executed every 2 minutes.

# config/schedule.rb
# ....
every 2.minute do
  rake 'whenever_call'
end

Now, we have to update our crontab file.

whenever --update-crontab

If we list our cron jobs in the crontab file, we will see something like the following.

# crontab file
0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58 * * * * /bin/bash -l -c 'cd OUR_PROJECT_PATH && RAILS_ENV=production bundle exec rake whenever_call --silent'

If we see in our production logs, we can see the following.

# log/production.log
I, [2020-11-15T20:50:02.590009 #53971]  INFO -- : Whenever task
I, [2020-11-15T20:52:02.914487 #54387]  INFO -- : Whenever task

As, you can see the logs have 2 minutes of difference.

However, you can see that the task is logging into our production.log. If you want to run the cron jobs in development environment, we can use the following.

whenever --update-crontab --set environment=development

Of course, we could specify more when the task runs. Here are some examples:

Scheduling a task every day at 3:00am

# config/schedule.rb
# ....
every 1.day, at: '3:00 am' do
  rake 'whenever_call'
end

# crontab file
0 3 * * * /bin/bash -l -c 'cd OUR_PROJECT_PATH && RAILS_ENV=production bundle exec rake whenever_call --silent'

Scheduling a task every 2 days at 3:00am and 5:30pm

# config/schedule.rb
# ....
every 2.day, at: ['3:00 am', '5:30 pm'] do
  rake 'whenever_call'
end

# crontab file
0 3 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31 * * /bin/bash -l -c 'cd OUR_PROJECT_PATH && RAILS_ENV=production bundle exec rake whenever_call --silent'

30 17 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31 * * /bin/bash -l -c 'cd OUR_PROJECT_PATH && RAILS_ENV=production bundle exec rake whenever_call --silent'

Scheduling a task on monday and sunday at 6:00pm

# config/schedule.rb
# ....
every [:monday, :sunday], at: '6:00 PM' do
  rake 'whenever_call'
end

# crontab file
0 18 * * 1,0 /bin/bash -l -c 'cd OUR_PROJECT_PATH && RAILS_ENV=development bundle exec rake whenever_call --silent'

If you want to clear the contents of the crontab file, you can also use the following command.

# Clear crontab
whenever -c

Final Words

Thanks for reading this post and you can find more info about whenever in its official github repo.

If you are also interested in know how to create scheduled jobs in Elixir, I recommend you this amazing post 3 ways to schedule tasks in Elixir I have learned in 3 years working with it.

Send emails with Python and Gmail

Brayan Vasquez — Sat, 03 Oct 2020 21:17:47 +0000

Hi Everyone!. In this post, I want to share with you a little guide that will show you how to send emails using Python and Gmail.

Requirements

Python (I use Python 3.8.2)
Pip (I use Pip 20.1.1)

Setup Project

To create our project we are going to use virtualenv, to create an isolated python environment for this project. However, you can also use pyenv or venv.

So, first, we have to install venv.

pip3 install virtualenv

Now, we have to create the project folder and set up the virtualenv.

# Creating a project folder
mkdir emails-example
cd emails-example

# Creating the virtual environment
virtualenv env

# Activate the virtual environment
source env/bin/activate

# Create our main file
touch main.py

NOTE: To exit the environment you just have to write deactivate.

Setup dotenv

Before starting to write code, we need to install the package python-dotenv, to manage environment variables, where we will put our Gmail credentials. We'll use .env files to easily configure the project and to avoid sharing sensitive info in our code.

pip install -U python-dotenv

Ok, now we should test if we can use the package. Create a file called .env.

touch .env

Create a test variable in our .env file.

TEST="my test variable"

Import the dotenv package and load the variables.

# main.py
# Import section ....
import os
from dotenv import load_dotenv

# Loading ENV variables
load_dotenv()

# Obtain our TEST variable
print(os.getenv('TEST'))

Run the script.

python main.py
# my test variable

Configure our Gmail account

To use the Gmail SMTP, we need to allow external apps in our Gmail account. So, we have to go to our account settings.

Click on the Security option.

Scroll down until you see the Less secure app access section, and click on Turn on access.

Click the switch button to turn ON the configuration.

Send basic emails

Now that we have configured our Gmail account, we can start writing code. First, we must import the python smtplib client, which will help us to send our emails.

# main.py
# Import section ....
from smtplib import SMTP, SMTPException # Import SMTP module
# ....

We will create some environment variables that we need to configure our SMTP client.

# .env

SENDER="YOUR GMAIL EMAIL"
PASSWORD="YOUR GMAIL PASSWORD"
RECEIVERS="A LIST OF EMAILS TO SEND THE MESSAGE, SEPARATED USING ','"
HOST="smtp.gmail.com"
PORT="587"

Now, we can set some constants using the environment variables defined before.

# main.py

# Constants section ....

# GMAIL account sender
SENDER = os.getenv('SENDER')
PASSWORD = os.getenv('PASSWORD')

# Accounts receivers
RECEIVERS = os.getenv('RECEIVERS').split(',')

# SMTP server options
HOST = os.getenv('HOST')
PORT = os.getenv('PORT')

# ....
# SMTP object
SMTP_OBJECT = SMTP(host=HOST, port=PORT)

Ok, We will create a base function to reuse in the other functions and avoid code duplication.

# main.py

# Methods section ....

# Base function
def send_email(message=""):
    """
    Send an email using the credentials defined before

    Parameters
    ----------
    message : str
        content to send in the message
    """
    try:
        SMTP_OBJECT.ehlo()
        SMTP_OBJECT.starttls()
        SMTP_OBJECT.login(SENDER, PASSWORD)
        SMTP_OBJECT.sendmail(SENDER, RECEIVERS, message)
        SMTP_OBJECT.quit()
        print("Successfully sent email")
    except SMTPException:
        print ("Error: unable to send email")

ehlo() Open a transmision using the command EHLO. Usually this method is called automatically when use sendmail() function. We also can use the function ehlo_or_helo_if_needed() for this purpose.
starttls() Uses the TLS protocol in the connection.
login() Login on the SMTP server.
sendmail() Sends our email.
quit() Terminate the session and close the connection.

Once we have the base function we can create our basic_mail function.

# main.py
# Methods section ....

def basic_email(message = ""):
    """
    Basic email with plain text message
    """
    send_email(message)

Our main function will be the following.

# main.py
# Import section ....
import sys

# Main section ...
if __name__ == "__main__":
    # Message to send
    message = """
    this message is sent from python for testing purposes
    """

    if len(sys.argv)> 1 :
        if sys.argv[1] == '--help':
            print('Info: ')
            print('--help List the options to send an email')
            print('--basic Sends a plain text email')
            print('--txt Send an email from a text file content')
            print('--attach Send an email with an attachment')
        elif sys.argv[1] == '--basic':
            print("Sending a plain text email")
            basic_email(message)
    else:
        print("Please give the type of message to send.")
        print("For help execute `python main.py --help`")

We can test our function by executing the following command in our terminal.

python main.py --basic

# Sending a plain text email
# Successfully sent email

Send email from TXT file

Here, we will send a message from a .txt file. First, we have to import some useful functions.

# main.py
# Import section ....
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.base import MIMEBase
import email.encoders

MIMEBase This is the base class for all the MIME-specific subclasses.
MIMEMultipart To send messages divided in multiple messages. Usually used for attachments.
MIMEText To work with plain text files.

Now, We can create our function to send emails attaching a text file.

# main.py

# Methods section ....
def send_from_txt():
    """
    Send an email reading the content message from a txt file
    """
    message = MIMEMultipart('alternative')
    message['Subject'] = 'TXT file content'
    message['From'] = SENDER
    body = "Email message body"
    content = MIMEText(body, 'plain')
    message.attach(content)

    # process text file
    file_open = open('text.txt', 'rb')
    file_content = MIMEText(_text=file_open.read(), _charset='utf-8')
    file_open.close()
    message.attach(file_content)

    # Send email
    send_email(message.as_string())

Add the option to our main function.

# main.py

# Main section ...
if __name__ == "__main__":
    # ....

    if len(sys.argv)> 1 :
        # if ....
        elif sys.argv[1] == '--txt':
            print("Sending an email from a text file content")
            send_from_txt()
    else:
        # ....

Create a .txt file with a message.

# Creating file
touch text.txt

# Edit the file
nano text.txt

# Put the following message
Message from a TXT file

We can test our function by executing the following command in our terminal.

python main.py --txt

# Sending an email from a text file content
# Successfully sent email

Attaching files

Finally, we will send an email with a PDF attachment.

# main.py

# Methods section ....
def send_attachment():
    """
    Send an email with an attachment
    """
    message = MIMEMultipart('alternative')
    message['Subject'] = 'Attachment'
    message['From'] = SENDER

    attachment = MIMEBase('application', 'octet-stream')
    attachment.set_payload(open('file.pdf', 'rb').read())
    attachment.add_header('Content-Disposition', 'attachment; filename="file.pdf"')

    email.encoders.encode_base64(attachment)
    message.attach(attachment)

    # Send email
    send_email(message.as_string())

Add the option to our main function.

# main.py

# Main section ...
if __name__ == "__main__":
    # ....

    if len(sys.argv)> 1 :
        # if ....
        elif sys.argv[1] == '--attach':
            print("Sending an email with an attachment")
            send_attachment()
    else:
        # ....

We can test our function by executing the following command in our terminal.

python main.py --attach

# Sending an email with an attachment
# Successfully sent email

NOTE: To test this method we have to put in our project folder a file called file.pdf.

Final Words

Thanks for reading this post and don't forget to turn off the Less secure app access configuration.

You can find the code of this guide here.

Create PDFs using Python and xhtml2pdf

Brayan Vasquez — Sun, 27 Sep 2020 23:51:55 +0000

Hi Everyone!. In this post, I want to share with you a little guide that will show you how to create pdf files using Python and xhtml2pdf.

The xhtml2pdf lib is used to create pdf files from HTML files. It's just a guide that I made for myself, but I want to share it with you.

WARNING: Also, this is a guide I did with experimental purposes, I didn't use it in a production environment. Therefore, you must have in mind that its use in production could have issues. A better alternative to create PDF files is http://weasyprint.org/.

Requirements

Python (I use Python 3.8.2)
Pip (I use Pip 20.1.1)

Setup Project

To create our project we are going to use virtualenv, to create an isolated python environment for this project. However, you can also use pyenv or venv.

So, first, we have to install venv.



pip3 install virtualenv

Now, we have to create the project folder and set up the virtualenv.



# Creating a project folder
mkdir pdfs-example
cd pdfs-example

# Creating the virtual environment
virtualenv env

# Activate the virtual environment
source env/bin/activate

# Create our main file
touch main.py

NOTE: To exit the environment you just have to write deactivate.

Install dependencies

To create our PDF files we need to install the xhtml2pdf library. This library, also depends on html5lib and reportlab.



pip install reportlab # https://pypi.org/project/reportlab/
pip install html5lib # https://pypi.org/project/html5lib/
pip install xhtml2pdf

NOTE: We need an xhtml2pdf version higher than 0.1a1 to work with Python3.

We can see the installed dependencies with the following command.



# Installed dependencies
pip freeze

# The above mentioned command will list something like the following
html5lib==1.1
Pillow==7.2.0
PyPDF2==1.26.0
reportlab==3.5.50
six==1.15.0
webencodings==0.5.1
xhtml2pdf==0.2.4

We can also export our dependencies.



pip freeze > requirements.txt

And install our dependencies from a requirements.txt file.



pip install -r requirements.txt

Generate PDF from string

Now that we have the necessary modules installed, we can start writing code. First, we must import the xhtml2pdf module, which will help us to create our PDF files.



# main.py
# import section ....
from xhtml2pdf import pisa             # import python module
# ....

Now, we can define some constants.



# main.py

# Constants section ....
# Content to write in our PDF file.
SOURCE = "<html><body><p>PDF from string</p></body></html>"

# Filename for our PDF file.
OUTPUT_FILENAME = "test.pdf"
# ....

Ok, We will create a base function to reuse in the other functions and avoid code duplication.



# main.py

# Methods section ....
def html_to_pdf(content, output):
    """
    Generate a pdf using a string content

    Parameters
    ----------
    content : str
        content to write in the pdf file
    output  : str
        name of the file to create
    """
    # Open file to write
    result_file = open(output, "w+b") # w+b to write in binary mode.

    # convert HTML to PDF
    pisa_status = pisa.CreatePDF(
            content,                   # the HTML to convert
            dest=result_file           # file handle to recieve result
    )           

    # close output file
    result_file.close()

    result = pisa_status.err

    if not result:
        print("Successfully created PDF")
    else:
        print("Error: unable to create the PDF")    

    # return False on success and True on errors
    return result

# ....

Once we have the base function we can create our from_text function.



# main.py

# Methods section ....
def from_text(source, output):
    """
    Generate a pdf from a plain string

    Parameters
    ----------
    source : str
        content to write in the pdf file
    output  : str
        name of the file to create
    """
    html_to_pdf(source, output)

# ....

Our main function will be the following.



# main.py
# import section ....
import sys

# Main section ...
if __name__ == "__main__":
    if len(sys.argv)> 1 :
        if sys.argv[1] == '--help':
            print('Info: ')
            print('--help List the options to send an email')
            print('--text Create a PDF file from a string')
            print('--template Create a PDF file from a template')
        elif sys.argv[1] == '--text':
            print("Creating a PDF file from a string")
            from_text(SOURCE, OUTPUT_FILENAME)
    else:
        print("Please give the type of message to send.")
        print("For help execute `python main.py --help`")

We can test our function by executing the following command in our terminal.



python main.py --text

# Creating a PDF file from a string
# Successfully created PDF

Generate PDF from template

Here, we will generate a PDF file using an HTML template. We have to keep in mind that xhtml2pdf supports until HTML4. So, first, we have to create an HTML file that will behave as a template for our PDF file.



touch template.html

And we will define a simple html template.



<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>PDF Generator</title>
</head>
<body>
    <h1 style="color:red;">First PDF</h1>
    <h2 style="color:blue;">PDF with html template</h2>
    <p>John</p>
    <p>Snow</p>
    <p>35</p>
</body>
</html>

Create a new constant to define our template file.



# main.py

# Constants section ....
# Template file name
TEMPLATE_FILE = "template.html"
# ....

Now, We can create our function to read the template and create the PDF file.



# main.py

# Methods section ....
def from_template(template, output):
    """
    Generate a pdf from a html file

    Parameters
    ----------
    source : str
        content to write in the pdf file
    output  : str
        name of the file to create
    """
    # Reading our template
    source_html = open(template, "r")
    content = source_html.read() # the HTML to convert
    source_html.close() # close template file

    html_to_pdf(content, output)

# ....

Add the option to our main function.



# main.py

# Main section ...
if __name__ == "__main__":
    # ....

    if len(sys.argv)> 1 :
        # if ....
        elif sys.argv[1] == '--template':
            print("Creating a PDF file from a template")
            from_template(TEMPLATE_FILE, OUTPUT_FILENAME)
    else:
        # ....

We can test our function by executing the following command in our terminal.



python main.py --template

# Creating a PDF file from a template
# Successfully created PDF

Final Words

Thanks for reading this post and you can find the code of this guide here.

Consume APIs using Python and requests

Brayan Vasquez — Sun, 20 Sep 2020 22:35:38 +0000

Hi Everyone!. In this post, I want to share with you a little guide that will show you how to consume an APIs using Python and requests.

We will use the following API, https://jsonplaceholder.typicode.com/. That is a simple API for posts.

Requirements

Python (I use Python 3.8.2)
Pip (I use Pip 20.1.1)

Setup Project

To create our project we are going to use virtualenv, to create an isolated python environment for this project. However, you can also use pyenv or venv.

So, first, we have to install virtualenv.

pip3 install virtualenv

Now, we have to create the project folder and set up the virtualenv.

# Creating a project folder
mkdir apis-example
cd apis-example

# Creating the virtual environment
virtualenv env

# Activate the virtual environment
source env/bin/activate

# Create our main file
touch main.py

NOTE: To exit the environment you just have to write deactivate.

Install dependencies

To make HTTP requests we will use the requests module. We can install this module using the following command.

pip install requests

We can see the installed dependencies with the following command.

# Installed dependencies
pip freeze

# The above mentioned command will list something like the following
certifi==2020.6.20
chardet==3.0.4
idna==2.10
requests==2.24.0
urllib3==1.25.10

We can also export our dependencies.

pip freeze > requirements.txt

And install our dependencies from a requirements.txt file.

pip install -r requirements.txt

List posts

Now that we have the necessary modules installed, we can start writing code. First, we must import the requests module, which will help us to consume the API.

# main.py
# import section ....
import requests            # import python module
import json
# ....

Now, we will define the base url.

# main.py

# Constants section ....
# API base URL
BASE_URL = "https://jsonplaceholder.typicode.com"

Ok, we will create a function called get_all that will show all posts.

# main.py

# Methods section ....
def get_all():
    """
    Make a GET request to the API rest to get all the items
    """
    url = BASE_URL + "/posts"
    response = requests.get(url)

    json_result = response.json()
    print(json_result)

Our main function will be the following.

# main.py
# import section ....
import sys

# Main section ...
if __name__ == "__main__":
    if len(sys.argv)> 1 :
        if sys.argv[1] == '--help':
            print('Info: ')
            print('--help List the options to send an email')
            print('--list Show all posts')
            print('--show Show a specific post')
            print('--create Create a post')
            print('--update Update a post')
            print('--delete Delete a post')
        elif sys.argv[1] == '--list':
            print("Listing all posts")
            get_all()
    else:
        print("Please give the type of message to send.")
        print("For help execute `python main.py --help`")

We can test our function by executing the following command in our terminal.

python main.py --list

# Listing all posts
# [{'userId': x, 'id': x, 'title': 'xxxxxxx', 'body': 'xxxxxxxxxx'}, ....]

Create post

Here, we will create a post using a POST request. First, we will create a method called create_post.

# main.py

# Methods section ....
def create_post():
    """
    Make a post request to the API rest to create an item
    """
    url = BASE_URL + "/posts"

    # Request headers
    headers = { "Content-type": "application/json; charset=UTF-8" }

    # Request body
    body = {
      "title": 'foo',
      "body": 'bar',
      "userId": 1
    }

    data = json.dumps(body) # parse a dictionary to json string format

    response = requests.post(url, headers=headers, data=data)

    json_result = response.json()

    print(json_result)

Add the option to our main function.

# main.py

# Main section ...
if __name__ == "__main__":
    # ....

    if len(sys.argv)> 1 :
        # if ....
        elif sys.argv[1] == '--create':
            print("Create a post")
            create_post()
    else:
        # ....

We can test our function by executing the following command in our terminal.

python main.py --create

# Create a post
# {'title': 'foo', 'body': 'bar', 'userId': x, 'id': x}

Show a post

Here, we will show a specific post using a GET request. We will create a method called show_post.

# main.py

# Methods section ....
def show_post(id=1):
    url = BASE_URL + "/posts/" + str(id)
    response = requests.get(url)

    json_result = response.json()
    print(json_result)

Add the option to our main function.

# main.py

# Main section ...
if __name__ == "__main__":
    # ....

    if len(sys.argv)> 1 :
        # if ....
        elif sys.argv[1] == '--show':
            print("Show a post")
            show_post(1)
    else:
        # ....

We can test our function by executing the following command in our terminal.

python main.py --show

# Show a post
# {'userId': x, 'id': x, 'title': 'xxxxxxxxx', 'body': 'xxxxxxxxxx'}

Update a post

Here, we will update a post using a PUT request. We will create a method called update_post.

# main.py

# Methods section ....
def update_post(id = 1):
    """
    Make a post request to the API rest to create an item
    """
    url = BASE_URL + "/posts/" + str(id)

    # Request headers
    headers = { "Content-type": "application/json; charset=UTF-8" }

    # Request body
    body = {
      "title": 'fooz',
      "body": 'barz',
      "userId": 1,
      "id": id
    }

    data = json.dumps(body) # parse a dictionary to json string format

    response = requests.put(url, headers=headers, data=data)

    json_result = response.json()

    print(json_result)

Add the option to our main function.

# main.py

# Main section ...
if __name__ == "__main__":
    # ....

    if len(sys.argv)> 1 :
        # if ....
        elif sys.argv[1] == '--update':
            print("Update a post")
            show_post(1)
    else:
        # ....

We can test our function by executing the following command in our terminal.

python main.py --update

# Update a post
# {'userId': x, 'id': x, 'title': 'xxxxxxxx', 'body': 'xxxxxxxx'}

Delete a post

Here, we will update a post using a DELETE request. We will create a method called delete_post.

# main.py

# Methods section ....
def delete_post(id = 1):
    url = BASE_URL + "/posts/" + str(id)
    response = requests.delete(url)

    json_result = response.json()
    print(json_result)

Add the option to our main function.

# main.py

# Main section ...
if __name__ == "__main__":
    # ....

    if len(sys.argv)> 1 :
        # if ....
        elif sys.argv[1] == '--delete':
            print("Delete a post")
            show_post(1)
    else:
        # ....

We can test our function by executing the following command in our terminal.

python main.py --delete

# Delete a post
# {'userId': x, 'id': x, 'title': 'xxxxxxxxxxx', 'body': 'xxxxxxxxxxx'}

Final Words

Thanks for reading this post and you can find the code of this guide here.

Integrate AndminLTE with Ruby On Rails 6

Brayan Vasquez — Mon, 27 Jul 2020 02:48:05 +0000

Hi everyone!, This is my first post in the DEV community, and also my first post in English (my native language is Spanish). So first, I want to apologize if I have errors in my writing.

In this post, I want to share with you a little guide that will show you how to integrate the AdminLTE template with Ruby on Rails 6. It's just a guide that I made for myself, but I want to share it with you.

Requirements

Ruby (I use ruby 2.7.1p83)
Ruby on Rails (I use Rails 6.0.3.2)
NodeJS.
Yarn.

Note: I advise you to install ruby using a version manager like rvm or rbenv. Also, I recommend the GoRails Tutorial that will guide you throughout the process.

Step 1: Setup Project

We are going to install the tools we need, before initializing the rails project.

# Using npm to install yarn
# You may have to run this command using sudo on Linux
npm install --global yarn

# Installing ruby using rvm. However, you can use the tool that you prefer
rvm install 2.7

# List ruby versions installed
rvm list

# Use a specific ruby version
rvm use 2.7

# Install bundler
gem install bundler

# Install Ruby on Rails v6
gem install rails -v 6.0.3.2

You can check the installed tools with the following commands.

# Checking yarn version
yarn -v

# Checking ruby version
ruby -v

# Checking bundler version
bundle -v

# Checking bundle version version
rails -v

Once you checked that you have the tools installed. Let's move to create the rails project.

rails new adminlte-rails-template

Step 2: Setup Controller

Here, we are going to create a controller in which we will place the AdminLTE template.

# First you have to move to the app directory
cd adminlte-rails-template/

# Generate a controller only with the action index
rails generate controller home index

Set the default Url in the config/routes.rb file.

# config/routes.rb
root 'home#index'

Run the project.

rails server

And you will see the following.

Step 3: Setup JQuery and Bootstrap

AdminLTE depends on JQuery and Bootstrap, so we have to install them. Rails 6 comes with webpacker, so we can install these dependencies using npm or yarn.

# For AdminLTE 2.4
yarn add bootstrap@^3.3.7 jquery@^3.2 popper.js@^1.16.1

# For AdminLTE 3
yarn add bootstrap jquery popper.js

Configure the Jquery and Popper aliases in the config/webpack/environment.js file.

const {environment} = require('@rails/webpacker')

const webpack = require('webpack')

environment.plugins.append('Provide',
    new webpack.ProvidePlugin({
        $: 'jquery',
        jQuery: 'jquery',
        Popper: ['popper.js', 'default']
    })
)

module.exports = environment

Import bootstrap into the app/javascript/packs/application.js file.

// app/javascript/packs/application.js
// ....
import 'bootstrap';

document.addEventListener("turbolinks:load", () => {
  $('[data-toggle="tooltip"]').tooltip()
});
// ....

Add the following to the config/webpacker.yml file.

resolved_paths: ['app/assets']

Create the directory app/javascript/stylesheets/ to put the style files here. And to use webpack to compile these assests.

mkdir app/javascript/stylesheets

Create the app/javascript/stylesheets/application.scss file.

touch app/javascript/stylesheets/application.scss

For AdminLTE 2.4

Import bootstrap css files into the app/javascript/packs/application.js file. I had some issues importing bootstrap into the app/javascript/stylesheets/application.scss file; However, since we are using webpack, we can import css files into a js file.

Note: You can also use sprockets for this step to avoid importing css files into js files.

import 'bootstrap/dist/css/bootstrap.css';
import 'bootstrap/dist/css/bootstrap-theme';
import '../stylesheets/application'; // This file will contain your custom CSS

For AdminLTE 3.0

Import bootstrap into the app/javascript/stylesheets/application.scss file.

// app/javascript/stylesheets/application.scss
@import "bootstrap";

Import the styles into the app/javascript/packs/application.js file.

// app/javascript/packs/application.js
// ......
import '../stylesheets/application'; // This file will contain your custom CSS

Now, you can run the project again.

rails server

And, look that the fonts have changed, using the bootstrap font styles.

Step 4: Install AdminLTE template

Install the adminlte package.

# AdminLTE 2.4 package
yarn add admin-lte@^2.4.18

# AdminLTE 3.0 package
yarn add admin-lte@^3.0

Import the AdminLTE scripts into the app/javascript/packs/application.js file.

// app/javascript/packs/application.js
....
require('admin-lte');

For AdminLTE 2.4

Import the AdminLTE stylesheets into the app/javascript/packs/application.js file.

/* For AdminLTE 2.4 */
import "admin-lte/dist/css/AdminLTE.css";
import "admin-lte/dist/css/skins/_all-skins.css";

For AdminLTE 3.0

Import the AdminLTE stylesheets into the app/javascript/stylesheets/application.scss file.

/* For AdminLTE 3 */
@import "admin-lte";

We also need to install font-awesome.

# For AdminLTE 2.4
yarn add font-awesome@4.7.0

# For AdminLTE 3
yarn add @fortawesome/fontawesome-free

For AdminLTE 2.4

Import fontawesome styles into the app/javascript/packs/application.js file.

/* For AdminLTE 2.4 */
import "font-awesome/css/font-awesome.css";

For AdminLTE 3.0

Import fontawesome styles into app/javascript/stylesheets/application.scss

/* For AdminLTE 3 */
@import '@fortawesome/fontawesome-free';

For AdminLTE 3, import fontawesome scripts into app/javascript/packs/application.js

// ....
import "@fortawesome/fontawesome-free/js/all";

Step 5: Setup Layout

Change the app/views/layouts/application.html.erb file content.

For AdminLTE 2.4

<!DOCTYPE html>
<html>
  <head>
    <title>Rails6 AdminLTE 2.4</title>
    <%= csrf_meta_tags %>
    <%= csp_meta_tag %>

    <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
    <%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %>
  </head>

  <body class="hold-transition skin-blue sidebar-mini">
      <div class="wrapper">
        <%= render "base/header" %>
        <%= render "base/sidebar" %>

        <div class="content-wrapper">
          <section class="content-header">
            <h1>
              Page Header
              <small>Optional description</small>
            </h1>
            <ol class="breadcrumb">
              <li><a href="#"><i class="fa fa-dashboard"></i> Level</a></li>
              <li class="active">Here</li>
            </ol>
          </section>

          <section class="content container-fluid">
            <%= yield %>
          </section>
        </div>

        <%= render "base/footer" %>
        <%= render "base/control_sidebar" %>
      <div>
  </body>
</html>

For AdminLTE 3

<!DOCTYPE html>
<html>
  <head>
    <title> Rails6 AdminLTE 3.0</title>
    <%= csrf_meta_tags %>
    <%= csp_meta_tag %>

    <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
    <%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %>
  </head>

  <body data-scrollbar-auto-hide="n" class="hold-transition sidebar-mini layout-fixed">
      <div class="wrapper">
        <%= render "base/header" %>
        <%= render "base/sidebar" %>

        <div class="content-wrapper">
          <div class="content-header">
            <div class="container-fluid">
              <div class="row mb-2">
                <div class="col-sm-6">
                  <h1 class="m-0 text-dark">Starter Page</h1>
                </div><!-- /.col -->
                <div class="col-sm-6">
                  <ol class="breadcrumb float-sm-right">
                    <li class="breadcrumb-item"><a href="#">Home</a></li>
                    <li class="breadcrumb-item active">Starter Page</li>
                  </ol>
                </div><!-- /.col -->
              </div><!-- /.row -->
            </div><!-- /.container-fluid -->
          </div>

          <div class="content container-fluid">
            <div class="container-fluid">
              <%= yield %>
            </div>
          </div>
        </div>

        <%= render "base/footer" %>
        <%= render "base/control_sidebar" %>
      <div>
  </body>
</html>

Structuring views

Create the folder app/views/base.

mkdir app/views/base

In the app/views/base, we are going to create a few files.

# AdminLTE header layout
touch app/views/base/_header.html.erb

# AdminLTE sidebar layout
touch app/views/base/_sidebar.html.erb

# AdminLTE footer layout
touch app/views/base/_footer.html.erb

# AdminLTE control-sidebar layour
touch app/views/base/_control_sidebar.html.erb

We will use the starter.html page to structure our views. You can find the starter page in node_modules/admin-lte/starter.html.

Copy the class="main-header" section into the app/views/base/_header.html.erb file.
Copy the class="main-sidebar ..." section into the app/views/base/_sidebar.html.erb file.
Copy the class="main-footer" section into the app/views/base/_footer.html.erb file.
Copy the class="control-sidebar ..." and class="control-sidebar-bg" sections into the app/views/base/_control_sidebar.html.erb.

Finally, Run the project again.

rails server

AdminLTE 2.4

AdminLTE 3.0

Final Words

If you read the whole post, thanks a lot. And again, sorry if I had some writing mistakes, I will try to improve that. Also, I'm open to any comments or suggestions.

You can find the code of this guide here. And, you can find the Rails 5 version in my blog, Integrate Ruby on Rails 5 and AdminLTE.

Thanks Again!.