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Ruby Loops

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For Loops

2:55 with Jason Seifer

There's another kind of loop in Ruby called the 'for' loop. The for loop is a common kind of loop in other programming languages but it functions a little bit differently in Ruby. A Ruby for loop is more of an iterator and functions internally like the each method.

A Note About For Loops

Most Ruby programmers don't use the for loop very often, instead preferring to use an "each" loop and do iteration. The reason for this is that the variables used to iterate in the for loop exist outside the for loop, while in other iterators, they exist only inside the block of code that’s running.

You can use whichever you prefer but it's important to know how for loops work in your career as a Ruby programmer.

Code Samples

The following for loop creates a Range class with the numbers 1 to 3 and then passes it to the block:

for item in 1..3 do
  puts "The current item is #{item}."
end

The for loop also works on arrays: 

for item in ["Programming", "is", "fun"]
  puts "The current item is #{item}."
end

It's important to note that the variable will exist outside of the for loop after it runs.

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    There's another kind of loop in Ruby called the for loop. 0:00
    The for loop is a common kind of loop in other programming languages. 0:03
    But it functions a little bit differently in Ruby. 0:07
    A Ruby for loop is more an iterator and 0:11
    functions internally very much like the each method. 0:14
    Okay, using the Ruby workspace, let's go ahead and create a New File. 0:19
    And we'll call this for_loop.rb. 0:23
    A for loop is pretty easy to write. 0:28
    We use the word for and then just like a y loop or 0:30
    any other loop where we're using an iterator, we can say for item, 0:34
    and then we use the word in, and now we create something called a range. 0:40
    And what this is gonna do, we'll say, for item in 1 to 10 do and 0:45
    end, and then we do anything inside this loop. 0:50
    "The current item is #{item}." 0:55
    Now this is something new that we haven't seen before. 1:01
    And this is called a range. 1:04
    A range is created by using two different objects. 1:06
    In this case, the objects are numbers. 1:12
    And then two dots. 1:14
    Let's gonna say take every item in between these two dots, and it's going 1:15
    to make something similar to an array out of it, which we can then iterate over. 1:21
    Let's run that and see what happens. 1:29
    And then we can see it goes through each item, from one to ten and says what it is. 1:32
    Let's change that to three. 1:44
    Okay, so we have three items, and that works with ranges, and the for 1:47
    loop also would work with an array. 1:52
    So let's go ahead and create one, say programming is fun. 1:57
    And, we can just print the same thing out. 2:06
    current item is #{item}. 2:11
    So when we run this again, we see both 1, 2, 3, and Programming is fun. 2:16
    Most Ruby programmers don't use the for 2:24
    loop very often, instead preferring to use an each loop and do iteration. 2:26
    The reason for this, is that the variables used to iterate in the for 2:31
    loop, exist outside the for loop, 2:35
    while in other iterators they exist only inside the block of code that's running. 2:38
    You can use whichever you prefer, but it's important to know how for 2:43
    loops work in a career as a Ruby programmer. 2:47
    Try practicing using for loops now, using workspaces. 2:50

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