How does the yield magic work in ActionView?

Question

I was looking at how content_for works and observed the block.call in the capture_erb_with_buffer method. It apparently magically writes to the buf

Answer 1

Simply:

calling yield in a method executes code that was passed to the method via a block.

For instance

def my_method
  yield
end

my_method { puts "Hello" }
my_method { puts "World" }

these 5 lines will produce the following output to the screen

Hello
World

See the following page for a nice discussion of yield in Ruby: Ruby Yield