Ruby assign context to lambda?

Question

Is it possible not to assign context to lambda?

For example:

class Rule
  def get_rule
    return lambda {puts name}
  end
end

class Person
  attr_accessor :name

  def init_rule 
    @name = "ruby"
    Rule.new.get_rule.call() # should say "ruby" but say what object of class Rull, does not have variable name
    # or self.instance_eval &Rule.new.get_rule
  end
end

My target is -> stored procedure objects without contexts, and assign context before call in specific places. Is it possible?

Answer 1

A bit late to party, but here's an alternate way of doing this by explicitly passing the context to the rule.

class Rule
  def get_rule
    return lambda{|context| puts context.name}
  end
end

class Person
  attr_accessor :name
  def init_rule
    @name = "ruby"
    Rule.new.get_rule.call(self)
  end
end

Person.new.init_rule
#=> ruby

Answer 2

In the spirit of being really late to the party ;-)

I think the pattern that you are using here is the Strategy pattern. This separates the concerns between the code that changes "rules" and the part that is re-used "person". The other strength of this pattern is that you can change the rules at run-time.

How it could look

class Person
  attr_accessor :name

  def initialize(&rules)
    @name = "ruby"
    instance_eval(&rules)
  end
end

Person.new do 
  puts @name
end

=> ruby

Answer 3

Yeah, but be careful with it, this one is really easy to abuse. I would personally be apprehensive of code like this.

class Rule
  def get_rule
    Proc.new { puts name }
  end
end

class Person
  attr_accessor :name

  def init_rule 
    @name = "ruby"
    instance_eval(&Rule.new.get_rule)
  end
end