The Book of Ruby

Look Familiar?

Now that you know what a block is, you may notice that you’ve seen them before. Many times. For example, you previously used do..end blocks to iterate over ranges like this:

(1..3).each do |i|
    puts(i)
end

You have also used do..end blocks to iterate over arrays (see for_each2.rb in for Loops):

arr = ['one','two','three','four']
arr.each do |s|
    puts(s)
end

And you have executed a block repeatedly by passing it to the loop method (see 3loops.rb in loop):

i=0
loop {
    puts(arr[i])
    i+=1
    if (i == arr.length) then
        break
    end
}

The previous loop example is notable for two things: It has no list of items (such as an array or a range of values) to iterate over, and it is pretty darn ugly. These two features are not entirely unrelated! The loop method ...