class method as hash value

Question

I have this working code:

class Server
  def handle(&block)
    @block = block
  end

 def do
   @block.call
 end
end

class Client
  def initialize
    @server = Server.new
    @server.handle { action }
  end

  def action
    puts "some"
  end

  def call_server
    @server.do
  end
end

client = Client.new
client.call_server

My Server will handle more then one action so I want to change code such way:

class Server
  def handle(options)
    @block = options[:on_filter]
 end

 def do
   @block.call
 end
end

class Client
  def initialize
    @server = Server.new

   my_hash = { :on_filter => action }
   @server.handle(my_hash)
  end

  def action
    puts "some"
  end

  def call_server
    @server.do
  end
end

client = Client.new
client.call_server

It is incorrect code because action() method calls on create my_hash, but if I try to modify code to:

my_hash = { :on_filter => { action } }

i get error message.

Is it possible to create hash with methods as hash values ?

Answer 1

Sure it's possible, but not exactly with methods (as methods aren't objects in Ruby), but with Proc objects instead. Take a look at this tutorial, for example.

In short, you should be able to achieve what you want by

my_hash = { :on_filter => Proc.new{action} }

in your Client#initialize.

Answer 2

When you want a method, in Ruby, you have to call... method :-)

my_hash = { :on_filter => { method(:action) } }

Note that your original code could have been written:

@server.handle(&method(:action))

This tells it to use the method action as the block parameter (which is why there is a &). Instead, you were passing a block, so to be completely equivalent, you can now pass a block instead of a method if you prefer:

my_hash = { :on_filter => Proc.new{ action } }