Example 4

gistfile1.rb

#yield
class A
  def go(*attrs)
    p "Before block"
    attrs.each do |attr|
      p yield(attr)
    end if block_given?
    p "After block"
  end
end
a=A.new
a.go "1","2" do |i|
  "ciao#{i}"
end

#&block
class B
  def go(*attrs, &block)
    p "Before block"
    attrs.each do |attr|
      p block.call(attr)
    end if block_given?
    p "After block"
  end
end
b=B.new
b.go "1","2" do |i|
  "ciao#{i}"
end

#alternativa con accesso diretto
class C
  attr_reader :attr
  def initialize
    @attr = ""
  end
  def go(*attrs, &block)
    p "Before block"
    attrs.each do |attr|
      @attr = attr
      p instance_eval(&block)
    end if block_given?
    p "After block"
    C.name
  end
end
c=C.new
c.go "1","2" do
  "ciao#{attr}"
end