元編程Ruby便捷方法

Question

在我的程序中，我使用了一個狀態機，並有許多便利方法。我目前正在創建一個長長的「？」列表方法在模型中。

def purchase_ready? 
    self.current_state == 'purchase_ready' 
end 

def completed? 
    self.current_state == 'completed' 
end 

def region_prepared? 
    self.current_state == 'region_prepared' 
end 

什麼是元編程方式來做到這一點？

Answer 1

偷懶的方法是使用BasicObject#method_missing：

class State 
    def initialize state 
    @state = state 
    end 

    def method_missing name, *args 
    case name 
    when :purchase_ready, :completed, :region_prepared 
     @state == name 
    else 
     super 
    end 
    end 
end 

state = State.new(:purchase_ready) 
state.purchase_ready 
    #=> true 
state.completed 
    #=> false 
state.region_prepared 
    #=> false 
state.purchase_not_ready 
    #-> NoMethodError: undefined method `purchase_not_ready' for 
    # #<State:0x007f9dfb9674b8 @state=:purchase_ready> 

Answer 2

...這是一個答案！

由於這一博客：http://rohitrox.github.io/2013/07/02/ruby-dynamic-methods/

[:purchase_ready, :completed, :region_prepared].each do |method| 
    define_method "#{method}?" do 
     self.current_state == "#{method}" 
    end 
end