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Day 1 of #100DaysofCode - Understanding Iterators

sincerelybrittany profile image Brittany ・4 min read

#100DaysofCode (65 Part Series)

1) Day 1 of #100DaysofCode - Understanding Iterators 2) Day 2: #100DaysofCode - I updated to Catalina and All HELL Broke Loose 3 ... 63 3) Day 3: #100DaysofCode - Oh No, SQL 4) Day 4: #100DaysofCode - More Iterators 5) Day 5 - #100DaysofCode - Setting up a Sinatra App 6) Day 6 : #100DaysofCode - Setting up a Sinatra App : Part 2 - Config.ru 7) Day 7: #100DaysofCode - Setting up a Sinatra App - Part 3 8) Day 8: #100DaysofCode - Setting up Sinatra Database - Part 4 9) Day 9: #100DaysofCode - ActiveRecord and a Database 10) Day 10: #100DaysofCode - ActiveRecord and a Database 11) Day 11 : #100DaysofCode - RESTful Routes 12) Day 12: #100DaysofCode and Day 1 of #Javascript30 13) Day 13 - #100DaysofCode - #Javascript30 - Day 2 - CSS + JS Clock 14) Day 14: #100DaysofCode - Finalized my Sinatra Project -Security 15) #Day 15: #100DaysofCode - View my Sinatra Project 16) Day 16 - #100DaysofCode - Understanding MVC 17) Day 17 : #100DaysofCode - Knowing your Ruby Version & what Errno::EADDRINUSE means is important! 18) Day 18 of #100daysofCode - 3 challenges 19) Day 19 of #100daysofCode - Hashes 101 20) Day 20: #100DaysofCode - Practice makes perfect 21) Day 21 : #100DaysofCode - Cascading Style Sheets 101 22) Day 22 - #100daysofCode - CSS 101 Part 2 23) Day 23 - #100DaysofCode - Updated My Portfolio 24) Day 24 - #100DaysofCode - Practicing CSS Grid and Emmet Shortcuts on VSCode 25) Day 25 - #100DaysofCode - Intro to Rails 26) Day 26 - #100DaysofCode - Accessing Rails Commands 27) Day 27 : #100DaysofCode - Still reviewing the basic rails concepts . . . 28) Day 28 : #100DaysofCode - Adding Dev.to blogs to personal page 29) Day 29 : #100DaysofCode - Very Simple Rails App CRUD Practice 30) Day 30 : #100DaysofCode - Very basic rails continued 31) Day 31 - #100DaysofCode - Rails Routes 101 32) Day 32 : #100DaysofCode - Resources for learning to code 33) Day 33 - #100DaysofCode - Setting up my app on Heroku 34) Day 34 - #100DaysofCode - New/edit action versus create/update action 35) Day 35 : #100DaysofCode - A Code Challenge Completed 36) Day 36 - #100DaysofCode - Rails form_for versus form_tag 37) Day 37 : #100DaysofCode - 30 seconds of code 38) Day 38 - #100DaysofCode - Built my first basic rails application 39) Day 39 : #100DaysofCode - I updated my github profile page 40) Day 40 : #100DaysofCode - I need project ideas 41) Day 41 : #100DaysofCode - Collaboration 42) Day 42 : #100DaysofCode - The Planning of a Project 43) Day 43 : #100DaysofCode - The Amazing Faker Gem 44) Day 44 : #100DaysofCode - Code or Youtube? 45) Day 45 : #100DaysofCode - Basic Nested Forms 46) Day 46 : #100DaysofCode - Still reviewing form_for 47) Day 47 : #100DaysofCode - How do you code? 48) Day 48 : #100DaysofCode - Code Along 49) Day 49 : #100DaysofCode - Still Coding Along 50) Day 50 : #100DaysofCode - Keep Coding Along 51) Day 51 : #100DaysofCode - Code Along 52) Day 52 : #100DaysofCode - No Wifi, No Problem 53) Day 53: #100DaysofCode - Created user log in and log out functionality 54) Day 54 : #100DaysofCode -Review on setting up log in & sign up 55) Day 55 : #100DaysofCode - In Need of Advice on Reading Poorly Written Documentation 56) Day 56 : #100DaysofCode - A Tweet - Devise - Users 57) Day 57 : 100DaysofCode - Remembering to Git Commit Often 58) Day 58 : #100DaysofCode - Beginning to Learn Python 59) Day 59 : #100DaysofCode - Focused on My Rails Project 60) Day 60 : #100DaysofCode - CSS in Rails 61) Day 61 : #100DaysofCode - Omniauth? 62) Day 62 : #100DaysofCode - Sign in using a Third Party, Rails 63) Day 63 : #100DaysofCode - Refactoring 64) Day 64 : #100DaysofCode - Still Playing Around With OmniAuth 65) Day 65 : #100DaysofCode - Second Rails Project - I Want to Try Self-Referencing Tables
.map .each .find .select

Today I had my first project review and I have to say, I struggled. I got so nervous and I definitely understand imposter syndrome now! I knew what I wanted to say but at the time I could not think of any words to convey it. In addition, I struggled to understand or comprehend what was required from me while under the pressure. I know this is something I will need to work on, but for now, I want to review an area I needed to do more research on ITERATORS.

What are iterators:

According to GeeksforGeeks , the word iterate means doing one thing multiple times and that is what iterators do. Sometimes iterators are termed as the custom loops.

  • "Iterators" is the object-oriented concept in Ruby.
  • In more simple words, iterators are the methods which are supported by collections(Arrays, Hashes etc.). Collections are the objects which store a group of data members.
  • Ruby iterators return all the elements of a collection one after another.
  • Ruby iterators are "chainable" i.e adding functionality on top of each other.

Background:

During my project review, I was asked to create a class method that took an input as an argument and to see if the instance variable started with the input. Like so:

def self.get_articles(input)
    @@all.map { |x| x.title.start_with?(input)}
end

Sounds simple right? WRONG. I could not THINK. I was struggling with knowing if .map or .each was required. So I did some research on Iterators and this is what I discovered.

.EACH vs .MAP

Well use the following array as an example: array = [2, 4, 6]
With .map you are essentially creating a new array without manipulating the original array. So if I ran the following in irb:

array.map { |x| x * 3}

The output is a new array and the original array of [1, 2, 3] would not be affected. The output would be:

[6, 12, 18]

Unlike .each, which will return the same array, like so

array.each do |x|
      x * 3
 end

.each always returns the original, unchanged object. So the output would be the following:
[2, 4, 6]

So when working with arrays and iterators it is important to note that
.map gives you a new array with updated information, while .each does not edit the original array.

Other important iterators: .find and .select

.FIND
This method returns the first element in the array for which the block is not false, meaning that it meets the criteria. So if we had an array like so

arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

arr.find {|a| a > 5} 

The above returns the first element greater than 5 and nil if none satisfies the condition. So the output would be: 6

Now lets assume you had the following array = ["a", "b", "c", "d"] and you wanted to find where in the array the "c" was located. Luckily, you can also use the .find method to search by key and value like so:

array.find {|key, value| key == "c"} 

It returns an Array of the first match [key, value] that satisfies the condition and nil otherwise. So the output would be ["c", 3]

.SELECT
Just as it's name says, with this method you can select a subset of your original array, based on some criteria. As you are selecting only certain elements, the return data will still be an array, but with less or equal number of elements than your original array. So if we had the following

array = [1, 2, 3, 4, 5]

array.select { |num|  num.even?  }  

It returns a new array containing all elements of the array for which the given block returns a true value. So the output would be the following:
[2, 4]

.find gives you the first item to match your criteria and .select gives you a new array with all elements that fit your criteria.

My research on iterators has only begun as there are many others I want to learn now.

Such as:
Times Iterator
Upto Iterator
Downto Iterator
Step Iterator
Each_Line Iterator

But I will save those for another post.

This article was originally posted on Medium

I used the following sources/articles for guidance :

How to Use The Ruby Map Method (With Examples)

How To Use Array Methods in Ruby

Ruby iterators for beginners: return value cheat sheet

Ruby find_all vs select, what’s the deal?

How to Use the Ruby Map Method

Ruby | Types of Iterators

#100DaysofCode (65 Part Series)

1) Day 1 of #100DaysofCode - Understanding Iterators 2) Day 2: #100DaysofCode - I updated to Catalina and All HELL Broke Loose 3 ... 63 3) Day 3: #100DaysofCode - Oh No, SQL 4) Day 4: #100DaysofCode - More Iterators 5) Day 5 - #100DaysofCode - Setting up a Sinatra App 6) Day 6 : #100DaysofCode - Setting up a Sinatra App : Part 2 - Config.ru 7) Day 7: #100DaysofCode - Setting up a Sinatra App - Part 3 8) Day 8: #100DaysofCode - Setting up Sinatra Database - Part 4 9) Day 9: #100DaysofCode - ActiveRecord and a Database 10) Day 10: #100DaysofCode - ActiveRecord and a Database 11) Day 11 : #100DaysofCode - RESTful Routes 12) Day 12: #100DaysofCode and Day 1 of #Javascript30 13) Day 13 - #100DaysofCode - #Javascript30 - Day 2 - CSS + JS Clock 14) Day 14: #100DaysofCode - Finalized my Sinatra Project -Security 15) #Day 15: #100DaysofCode - View my Sinatra Project 16) Day 16 - #100DaysofCode - Understanding MVC 17) Day 17 : #100DaysofCode - Knowing your Ruby Version & what Errno::EADDRINUSE means is important! 18) Day 18 of #100daysofCode - 3 challenges 19) Day 19 of #100daysofCode - Hashes 101 20) Day 20: #100DaysofCode - Practice makes perfect 21) Day 21 : #100DaysofCode - Cascading Style Sheets 101 22) Day 22 - #100daysofCode - CSS 101 Part 2 23) Day 23 - #100DaysofCode - Updated My Portfolio 24) Day 24 - #100DaysofCode - Practicing CSS Grid and Emmet Shortcuts on VSCode 25) Day 25 - #100DaysofCode - Intro to Rails 26) Day 26 - #100DaysofCode - Accessing Rails Commands 27) Day 27 : #100DaysofCode - Still reviewing the basic rails concepts . . . 28) Day 28 : #100DaysofCode - Adding Dev.to blogs to personal page 29) Day 29 : #100DaysofCode - Very Simple Rails App CRUD Practice 30) Day 30 : #100DaysofCode - Very basic rails continued 31) Day 31 - #100DaysofCode - Rails Routes 101 32) Day 32 : #100DaysofCode - Resources for learning to code 33) Day 33 - #100DaysofCode - Setting up my app on Heroku 34) Day 34 - #100DaysofCode - New/edit action versus create/update action 35) Day 35 : #100DaysofCode - A Code Challenge Completed 36) Day 36 - #100DaysofCode - Rails form_for versus form_tag 37) Day 37 : #100DaysofCode - 30 seconds of code 38) Day 38 - #100DaysofCode - Built my first basic rails application 39) Day 39 : #100DaysofCode - I updated my github profile page 40) Day 40 : #100DaysofCode - I need project ideas 41) Day 41 : #100DaysofCode - Collaboration 42) Day 42 : #100DaysofCode - The Planning of a Project 43) Day 43 : #100DaysofCode - The Amazing Faker Gem 44) Day 44 : #100DaysofCode - Code or Youtube? 45) Day 45 : #100DaysofCode - Basic Nested Forms 46) Day 46 : #100DaysofCode - Still reviewing form_for 47) Day 47 : #100DaysofCode - How do you code? 48) Day 48 : #100DaysofCode - Code Along 49) Day 49 : #100DaysofCode - Still Coding Along 50) Day 50 : #100DaysofCode - Keep Coding Along 51) Day 51 : #100DaysofCode - Code Along 52) Day 52 : #100DaysofCode - No Wifi, No Problem 53) Day 53: #100DaysofCode - Created user log in and log out functionality 54) Day 54 : #100DaysofCode -Review on setting up log in & sign up 55) Day 55 : #100DaysofCode - In Need of Advice on Reading Poorly Written Documentation 56) Day 56 : #100DaysofCode - A Tweet - Devise - Users 57) Day 57 : 100DaysofCode - Remembering to Git Commit Often 58) Day 58 : #100DaysofCode - Beginning to Learn Python 59) Day 59 : #100DaysofCode - Focused on My Rails Project 60) Day 60 : #100DaysofCode - CSS in Rails 61) Day 61 : #100DaysofCode - Omniauth? 62) Day 62 : #100DaysofCode - Sign in using a Third Party, Rails 63) Day 63 : #100DaysofCode - Refactoring 64) Day 64 : #100DaysofCode - Still Playing Around With OmniAuth 65) Day 65 : #100DaysofCode - Second Rails Project - I Want to Try Self-Referencing Tables

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@sincerelybrittany

Web Developer | Software Engineer 👩🏾‍💻 | Determined | Music & Dance | #100DaysofCode | #WomenWhoCode

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