在Ruby中，我如何从派生类中覆盖同一方法的不同方法中调用基类方法？

huangapple
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英文:

In Ruby how do I call a base class method from a different method in a derived class that overrides that same method?

问题

如果我有一个具有方法'a'的基类和一个派生类，该派生类重新实现了方法'a'，我可以通过只调用super来从Derived.a中调用Base.a；如何从不同的派生类方法中调用基类'a'？

  1. class Base
  2.   def a
  3.     puts "hi, this is Base.a"
  4.   end
  5. end
  7. class Derived < Base
  8.   def a
  9.     puts "hi, this is Derived.a"
  10.   end
  12.   def b
  13.     # 这里是我想要调用Base.a的地方
  14.     super  # 这个工作
  15.   end
  16. end
英文:

If I have a base class with method 'a' and a derived class that reimplements method 'a', I can call Base.a from Derived.a by just calling super; how do I call the base class 'a' from a different derived class method?

  1. class Base
  2.   def a
  3.     puts &quot;hi, this is Base.a&quot;
  4.   end
  6. end
  8. class Derived &lt; Base
  9.   def a
  10.     puts &quot;hi, this is Derived.a&quot;
  11.   end
  13.   def b
  14.     # here is where I want to call Base.a
  15.     Base.a  # this doesn&#39;t work
  16.     
  17.   end
  18. end

答案1

得分: 6

你可以使用方法 Method#super_method：

  1. class Base
  2.   def a
  3.     puts "hi, this is Base.a"
  4.   end
  5. end
  7. class Derived < Base
  8.   def a
  9.     puts "hi, this is Derived.a"
  10.   end
  12.   def b
  13.     # 这里我想调用 Base.a
  14.     method(:a).super_method.call
  15.   end
  16. end
  18. Derived.new.b
  19. hi, this is Base.a

更一般地，你可以有参数和/或一个块：

  1. class Base
  2.   def c(x, &block)
  3.     puts "ho, this is Base.c"
  4.     block.call(3*x)
  5.   end  
  6. end
  8. class Derived < Base
  9.   def c(x, &block)
  10.     puts "ho, this is Derived.c"
  11.     block.call(x)
  12.   end  
  14.   def d(x, &block)
  15.     method(:c).super_method.call(x, &block)
  16.   end
  17. end
  19. Derived.new.d(5) { |x| puts "#{x} is a lot" }
  20. ho, this is Base.c
  21. 15 is a lot

你还可以这样做：

  1. class A
  2.   def a
  3.     "A.a"
  4.   end
  5. end
  7. class B < A
  8.   def a
  9.     "B.a"
  10.   end
  11. end
  13. class C<B
  14.   def a
  15.     "C.a"
  16.   end
  18.   def test
  19.     method(:a).super_method.super_method.call
  20.   end
  21. end
  23. C.new.test
  24. # => "A.a"
英文:

You can use the method Method#super_method:

  1. class Base
  2.   def a
  3.     puts &quot;hi, this is Base.a&quot;
  4.   end
  5. end

<!-->
class Derived < Base
def a
puts "hi, this is Derived.a"
end

  1.   def b
  2.     # here is where I want to call Base.a
  3.     method(:a).super_method.call
  4.   end
  5. end

<!-->
Derived.new.b
hi, this is Base.a

More generally, you could have arguments and/or a block.

  1. class Base
  2.   def c(x, &amp;block)
  3.     puts &quot;ho, this is Base.c&quot;
  4.     block.call(3*x)
  5.   end  
  6. end

<!-->
class Derived < Base
def c(x, &block)
puts "ho, this is Derived.c"
block.call(x)
end

  1.   def d(x, &amp;block)
  2.     method(:c).super_method.call(x, &amp;block)
  3.   end
  4. end

<!-->
Derived.new.d(5) { |x| puts "#{x} is a lot" }
ho, this is Base.c
15 is a lot

You could also do the following.

  1. class A
  2.   def a
  3.     &quot;A.a&quot;
  4.   end
  5. end

<!-->
class B < A
def a
"B.a"
end
end
<!-->
class C<B
def a
"C.a"
end
<!-->
def test
method(:a).super_method.super_method.call
end
end
<!-->
C.new.test
#=> "A.a"

答案2

得分: 6

alias_method可以做到这一点：

使new_name成为old_name方法的新副本。这可用于保留对被覆盖的方法的访问。

https://rubyapi.org/3.2/o/module#method-i-alias_method

  1. class Base
  2.   def a
  3.     puts "hi, this is Base.a"
  4.   end
  5. end
  7. class Derived < Base
  8.   alias_method :base_a, :a
  10.   def a
  11.     puts "hi, this is Derived.a"
  12.   end
  14.   def b
  15.     base_a
  16.   end
  17. end
  1. >> Derived.new.b
  2. hi, this is Base.a
  3. >> Derived.new.a
  4. hi, this is Derived.a
英文:

alias_method can do it:
> Makes new_name a new copy of the method old_name. This can be used to retain access to methods that are overridden.

https://rubyapi.org/3.2/o/module#method-i-alias_method

  1. class Base
  2.   def a
  3.     puts &quot;hi, this is Base.a&quot;
  4.   end
  5. end
  7. class Derived &lt; Base
  8.   alias_method :base_a, :a
  10.   def a
  11.     puts &quot;hi, this is Derived.a&quot;
  12.   end
  14.   def b
  15.     base_a
  16.   end
  17. end
  1. &gt;&gt; Derived.new.b
  2. hi, this is Base.a
  3. &gt;&gt; Derived.new.a
  4. hi, this is Derived.a

huangapple
  • 本文由 发表于 2023年7月14日 06:47:19
  • 转载请务必保留本文链接：https://go.coder-hub.com/76683707.html
  • ruby
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