Syntactic sugar for simple filtering. A halfway point between posts.select(&:published) and posts.select{|post| post.comments.any?}

instance_block.rb

# before - each object in the enumerable is passed to the block
posts.select { |post| post.comments.any? }

class Array
  def select(&blk)
    if blk.arity == 0
      super { |obj| obj.instance_exec &blk }
    else
      super
    end
  end
end

# after - block is optionally evaluated in the context of each object in the enumerable
posts.select { |post| post.comments.any? }
posts.select { comments.any? }

instance_do.rb

# basically the same setup with a different method name for different use case

class Object
  def do(&blk)
    instance_exec &blk
  end
end

# before - reference the object
foo.bar * foo.baz

# after
foo.do { bar*baz }