是否可以从Julia中的覆盖函数调用重载函数? [英] Is it possible to call an overloaded function from overwriting function in Julia?

问题描述

问题如下:

我有一个抽象类型MyAbstract和派生的复合类型MyType1和MyType2:

I have an abstract type MyAbstract and derived composite types MyType1 and MyType2:

abstract MyAbstract

type MyType1 <: MyAbstract
    somestuff
end

type MyType2 <: MyAbstract
    someotherstuff
end

我想为MyAbstract类型的对象指定一些常规行为，所以我有一个函数

I want to specify some general behaviour for objects of type MyAbstract, so I have a function

function dosth(x::MyAbstract)
    println(1) # instead of something useful
end

此常规行为足以满足MyType1的需要，但是当使用类型为MyType2的参数调用dosth时，我希望发生一些特定于MyType2的事情，当然，我想重用现有的代码，所以我尝试了以下操作，但是没有用:

This general behaviour suffices for MyType1 but when dosth is called with an argument of type MyType2, I want some additional things to happen that are specific for MyType2 and, of course, I want to reuse the existing code, so I tried the following, but it did not work:

function dosth(x::MyType2)
    dosth(x::MyAbstract)
    println(2)
end

x = MyType2("")
dosth(x) # StackOverflowError

这意味着Julia在一段时间内没有意识到我试图将x像其超类型"一样对待.

This means Julia did not recognize my attempt to treat x like its "supertype" for some time.

是否可以从Julia的覆盖函数中调用重载函数?我该如何优雅地解决这个问题?

Is it possible to call an overloaded function from the overwriting function in Julia? How can I elegantly solve this problem?

推荐答案

您可以使用 invoke函数

You can use the invoke function

function dosth(x::MyType2)
    invoke(dosth, (MyAbstract,), x)
    println(2)
end

使用相同的设置，它给出以下输出，而不是堆栈溢出:

With the same setup, this gives the follow output instead of a stack overflow:

julia> dosth(x)
1
2

可以在此处找到有关替换或改进invoke的界面的讨论.我的建议是使语法非常接近您在问题中所写的内容:

Discussion can be found here on replacing or improving the interface to invoke. My proposal would make the syntax very close to what you wrote in your question:

function dosth(x::MyType2)
    @invoke dosth(x::MyAbstract)
    println(2)
end

如果您对使用比调用"更直观的名称有任何想法，请在下面发表评论.

If you have any thoughts on what a more intuitive name than "invoke" would be, please post a comment below.

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