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Rails 中alias Alias_method Alias_method_chain的使用

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首先看一下alias的用法，上一个实例是明了
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class Dog
  def say
          puts  "say hello"
  end
 alias :wang :say
end

dog = Dog.new
dog.wang

=> say hello

在类中可以将一个实例方法重新命名,注意的是新方法在前面，用空格格开

alias_method的用法，

和alias一样，只是他是module的一个私有方法，而且它的方法名可以是字符中，而alias不行，看代码

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module Dog
  def say
          puts  "say hello"
end

alias_method "wang", "say"
#alias_method :wang, :say
end

class Animal
  include Dog
end

a = Anima.new
a.wang

=>say hello

alias_method_chain 是ActiveSupport的一个公有实例方法，用法和alias_method是一样的，这里不举例，最后附上alias_method_chain的源码
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def alias_method_chain(target, feature)
  # Strip out punctuation on predicates or bang methods since    
  # e.g. target?_without_feature is not a valid method name.    
  aliased_target, punctuation = target.to_s.sub(/([?!=])$/, ''), $1
  yield(aliased_target, punctuation) if block_given?
  with_method, without_method = "#{aliased_target}_with_#{feature}#{punctuation}", "#{aliased_target}_without_#{feature}#{punctuation}"
  alias_method without_method, target
  alias_method target, with_method
  case
    when public_method_defined?(without_method)
      public target
    when protected_method_defined?(without_method)
      protected target
    when private_method_defined?(without_method)
    private target
  end
end

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