Question

I am interested whether this can be done and what the syntax would be. I’m at:

def say_it
  puts "before"
  yield("something here")
  puts "after"
end

say_it do |val|
  puts "here is " + val
  yield("other things") # ???
end 

thinking probably no but maybe if block gets converted to a Proc?

thx in advance

Answer 1

A yield only makes sense from within a method that takes a block.

And yes, they can nest. Note that:

1. Traversal still happens along the stack; and
2. Blocks (and yield) are strictly tied to methods.

Example:

def double(x)
    yield x * 2
end

def square_after_double(x)
    double(x) do |r|
       # Yields to the block given to the current method.
       # The location of the yield inside another block
       # does not change a thing.
       yield r * r
    end
end

square_after_double(3) do |r|
  puts "doubled and squared: " + r.to_s
end