通过在模块中混合来覆盖类的实例方法 [英] Overriding instance methods of a class by mixing in a module

问题描述

给出一个类A和一个模块B，将B的实例方法混合在一起，以使其覆盖A的相应实例方法.

Given a class A and a module B, mixin the instance methods of B so that it overrides the correspnding instance methods of A.

module B
  def method1
    "B\#method1"
  end

  def method2
    "B\#method2"
  end
end

class A
  def method1
    "A\#method1"
  end

  def method2
    "A\#method2"
  end

  # include B    does not override instance methods!
  #              (module gets mixed into the superclass)
end

puts A.new.method1   # want it to print out "B#method1"
puts A.new.method2   # want it to print out "B#method2"

推荐答案

您可以在包含B之前从A中删除B的每个方法.

You could remove each of B's methods from A before including B.

class A
  def method1
    "A\#method1"
  end

  def method2
    "A\#method2"
  end

  B.instance_methods(false).each { |method|
    remove_method(method) if instance_methods(false).include?(method)
  }
  include B
end

或从B内部:

module B
  def method1
    "B\#method1"
  end

  def method2
    "B\#method2"
  end

  def self.append_features(mod)
    instance_methods(false).each { |method|
      mod.send(:remove_method, method) if mod.instance_methods(false).include?(method)
    }
    super
  end
end

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