How does yield work with a block in Ruby?

Question

I'm trying to understand how yield works in Ruby?

def ablock
i = 1
j = 2
yield(i, j, 3, 4)
end

ablock do |x| puts x
end

This gives me an output of - 1 2 3 4

But,

def ablock
i = 1
j = 2
yield(i, j, 3, 4)
end

ablock do |x,y| puts x, y
end

Gives me only 1 2 as the output. Why don't 3 & 4 print?

http://stackoverflow.com/questions/3066703/blocks-and-yields-in-ruby — Joe, Sep 18 '14 at 22:21
I do not see the same results as you for the first example. When I run it with irb only see `1` printed. — Alex.Bullard, Sep 18 '14 at 22:39

Schylar · Accepted Answer · 2014-09-18T23:17:11.700

3

The answer is pretty simple. You have defined your block method correctly but when you go to give it a code block you only give it one variable to hold 4 objects. Instead, try giving it a variable for each object you are yielding!

def ablock
    i=1
    j=2
    yield(i,j,3,4)
end

ablock do |i,j,k,l|
    puts i
    puts j
    puts k
    puts l
end

If you would only like to use one variable in your code block you have to do multiple yield statements(one for each object).

def ablock
  i=1
  j=2
  yield(i)
  yield(j)
  yield(3)
  yield(4)
end

ablock do |i|
  puts i
end

Happy coding!

edited Sep 18 '14 at 23:17

answered Sep 18 '14 at 22:56

Schylar

774
1
5
13

You are right! It seems the online interpreter I was using was faulty. Thanks! – TheDareDevil Sep 18 '14 at 23:22
No problem! Mind if I ask which website you were using? – Schylar Sep 18 '14 at 23:23
It was this one - http://repl.it/ – TheDareDevil Sep 19 '14 at 14:26

How does yield work with a block in Ruby?

1 Answers1