Making things is only available inside Ruby blocks

Pass the object using the methods you want to use as an argument in the block. This is a pattern that is widely used in Ruby, for example, IO.open

or an XML constructor .

some_block do |thing|
    thing.available_only_in_block
    thing.is_this_here?
    thing.okay_cool
end

      

        
        
        
      

    

Note that you may be close to what you asked to use instance_eval

or instance_exec

, but this is generally a bad idea as it can have some pretty unexpected consequences.

class Foo
  def bar
    "Hello"
  end
end

def with_foo &block
  Foo.new.instance_exec &block
end

with_foo { bar }      #=> "Hello"
bar = 10
with_foo { bar }      #=> 10
with_foo { self.bar } #=> "Hello

      

        
        
        
      

    

If you pass an argument, you always know what you will be referring to:

def with_foo
  yield Foo.new
end

with_foo { |x| x.bar }      #=> "Hello"
bar = 10
x = 20
with_foo { |x| x.bar }      #=> "Hello"