meet it

runs the block someone handed to your method.

You have used blocks with each and times since Level 1. Now you write the method on the other side. Inside your method, yield runs whatever block the caller attached, then your method carries on from the next line. It is like a recipe saying: now add your favourite topping.

yield can hand values to the block, and they arrive between its bars: yield(2.5, 3) fills |coffee, cake|. The block's last line comes back as the answer of yield, so your method can use it.

Calling yield when no block was attached crashes with . When the block is optional, ask first.

def receipt(shop)
  puts "== #{shop} =="
  total = yield(2.5, 3)
  puts "Total: #{total}"
end
receipt("Corner Cafe") do |coffee, cake|
  coffee + cake
end

Curly braces { |word| ... } work like do and end, and most Rubyists use them for one-line blocks.

guess first

Two yields and a last line. What will this show?

Guess before you run it. Wrong guesses are how you learn, and nothing is marked.

def twice
  yield "first"
  yield "second"
  "done"
end
result = twice { |word| puts word.upcase }
puts result

your turn

Your turn. Make an announcer that takes a block.

Fill the first blank so the method runs the block and hands it name. Then type a winner's name in the second blank and press run.

Your code

press run to see what happens

fix it

The cake has no block, and the program falls over. Fix it.

Broken code to fix

press run to see what happens

The tea line works. The cake call has no block. What does yield do then?
With no block attached, yield raises LocalJumpError. Only yield when there is a block.
Add if block_given? to the end of line 3, then press run.

nailed it

your methods can take blocks now. :D

yield runs the block the caller attached.
Values after yield arrive between the block's bars.
Check block_given? when the block is optional.

new words in your collection

yield
block_given?
LocalJumpError

This lesson isn’t saved. A free account remembers every lesson you finish.

yield runs the block someone handed to your method.

Two yields and a last line. What will this show?

Your turn. Make an announcer that takes a block.

The cake has no block, and the program falls over. Fix it.

your methods can take blocks now. :D

runs the block someone handed to your method.