DEV Community: Nitin Reddy

Ruby: IRB tab-autocomplete

Nitin Reddy — Fri, 19 Feb 2021 06:34:46 +0000

Ruby's IRB is a pretty good environment to quickly test a snippet of code. And when you want to test a snippet of code, you do not necessarily know all of the methods and properties for the objects you are working with. If only there were a tab code-complete feature in IRB.

...which has been available in IRB since too-long-ago-to-remember.

What you neeed to do is run this one-line require and then you get autocomplete:

require 'irb/completion'

For instance, type

'red'.cap

and then press Tab. Auto-complete! :-)

HTTP 418 - I'm a Tea Pot

Nitin Reddy — Fri, 01 Jan 2021 17:25:25 +0000

We have an HTTP response code 418 for tea pots. Why would a tea pot be listening on TCP port 80? 🤔

Workaround for "rails g scaffold" hangs

Nitin Reddy — Sat, 26 Dec 2020 17:35:46 +0000

If you are running a "rails g scaffold ..." and have the command hanging with no visible sign of activity, Spring is likely playing havoc.

Rails Spring is a preloader for the Rails framework. If you execute a "spring stop" and re-run the scaffold command, it should work. However, having to stop Spring after every command is going to get aggravating so there's an environment variable you can set - DISABLE_SPRING.

Run "spring stop" (if it is already running) and then define the DISABLE_SPRING variable like this on a bash prompt:
export DISABLE_SPRING=true

GitHub "main" branch

Nitin Reddy — Sun, 25 Oct 2020 16:48:16 +0000

If you have created a new GitHub repository recently, you may have noticed that the default branch name is "main" instead of "master". To change the default branch from "main" back to "master" (after creating the "master" branch), and navigate to the Settings > Branches page.

The master-slave terminology has been removed from most software (MongoDB recently renamed the "rs.slaveOk" command to "rs.secondaryOk") and GitHub is doing its part in promoting equality.

Creating Certificates with certie

Nitin Reddy — Sun, 23 Aug 2020 19:27:09 +0000

To setup TLS/SSL for web servers, X.509 client authentication, or even for database servers, you need to have certificate files. The quickest way to generate them, assuming you are on MacOS/Linux, is with certie.

Installing certie is simple:

sudo gem install certie

Following the installation, generating the certificates is as simple as:

certie dev.mymachine.local

This creates a root certificate and a server certificate in PEM format within the current directory.

You may want to change the subject prefix by editing the ".certie_subjprefix" file in your home directory. Note that if you change the subject prefix, you would need to start over (delete the contents of the current directory, or create a new directory).

Dependencies

If you were unable to successfully execute "gem install certie" above, you likely need to install Ruby and OpenSSL dependencies.

If you are on RedHat, you may need to install build tools and Ruby:

sudo yum groupinstall -y "Development Tools"
sudo yum install -y ruby-devel openssl-devel

For Ubuntu/Debian, the dependencies are installed with:

sudo apt install -y ruby-dev libssl-dev build-essential

Building a Desktop GUI App with Ruby

Nitin Reddy — Sat, 15 Aug 2020 07:15:19 +0000

It's 2020 and just about every other blog post on software development captures experiences in web development. Desktop development is as uncommon as spotting an orangutan on a beach. In this blog post, we are going to briefly look at how we can build a desktop user interface using Ruby and the GTK3 library. Also, this post assumes that you are using Mac OS.

To get started, you would need to install the following dependencies. GTK3 is available as a brew package and so is the Glade user interface designer. We will use the gtk3 gem for Ruby.

brew install gtk+3
brew install glade
gem install gtk3

If you did any kind of programming with Windows Forms, AWT, Swing, native iOS, or native Android, then you have used a GUI library that introduces you to the basics of building desktop user interfaces - they involve adding controls/widgets into layout containers that fit into a top-level window/frame.

Within the UI heirarchy, Window is a top-level container. You can set properties such as the size, position, and border of windows and can add child widgets to it. The following code creates a new Window object, sets the size property, and adds a delete event handler.

require 'gtk3'

window = Gtk::Window.new("My Window")
window.set_size_request(300,200)
window.signal_connect "delete-event" do |e|
  Gtk.main_quit
end

Typically, you would use a layout manager within a window to help with the placement of widgets. Grid layout is pretty simple - all you would need to do is specify the column and row within which you want to place a widget, for instance a label. The code for this appears below.

grid = Gtk::Grid.new
label = Gtk::Label.new("Name")
grid.attach label, 0, 0, 1, 1

Let's do something useful by displaying IP addresses within the label:

require 'socket'
ips = Socket.ip_address_list
label.text = ips.map { |iter| iter.ip_address }.join ("\n")

Looks simple so far? We then put the grid into the window and display it on-screen.

window.add grid
window.show_all
Gtk.main

You now have a perfectly good way to see the IP addresses of the host you are running this code on. GTK includes lots of widgets from Entry (text boxes) to Notebooks (tabbed panels), which you can see on the widget gallery at:
https://developer.gnome.org/gtk3/stable/ch03.html

You can experiment with the code above by adding buttons:

button = Gtk::Button.new(:label => "Click Me")
button.signal_connect "clicked" do |e|
  puts "Hello"  # Displayed on the text console that you run the script from
end
grid.attach button, 0, 1, 1, 1

As the user interface gets more complex, you may want to use the Glade UI designer instead of hand-coding the interface.

Directories within root after upgrading to MacOS Catalina (10.15)

Nitin Reddy — Sun, 20 Oct 2019 19:16:34 +0000

After upgrading to MacOS Catalina, you would no longer be able to create directories in the root directory. On attempting to create a directory, you would see a “Read-only file system” error:

Nitins-MacBook-Pro:/ nitin$ sudo mkdir -p /data/db
Password:
mkdir: /data/db: Read-only file system
Nitins-MacBook-Pro:/ nitin$

Upon upgrading, directories existing within the root directory are moved to the path “/Users/Shared/Relocated Items/Security“ and a shortcut on the desktop named “Relocated Items” is created.

Also see: "Dedicated system volume" at https://www.apple.com/macos/catalina/features/

MacOS Catalina defaults to zsh

Nitin Reddy — Fri, 11 Oct 2019 15:24:18 +0000

If you are on MacOS, you have probably noticed that MacOS now has zsh as the default shell instead of bash. If you haven't, you are doing a great job of ignoring the motd on opening the terminal :-)

The default interactive shell is now zsh.
To update your account to use zsh, please run `chsh -s /bin/zsh`.
For more details, please visit https://support.apple.com/kb/HT208050.

MacOS had bash as the default shell for the Terminal since Panther (OS X 10.3). However, when bash v.4 was released under the GPL v3 license (previous versions of bash were released under the GPL v2 license), Apple decided to switch to zsh. bash is still available on Mojave (OS X 10.14) and Catalina (OS X 10.15) so your bash scripts would still run.

As a developer, the most obvious change is that for changes to the shell environment, you have to edit the .zshrc file instead of the .bashrc file and the .zprofile file instead of .bash_profile. The command history is in .zsh_history instead of .bash_history.