blocks|key|417500|text|这是可能的，但我不确定这是一种我推荐给初学者的技术。与其他情况一样，当您希望函数的选择取决于返回值的使用方式时，可以使用代理；首先定义像getChar和getInt这样的函数，然后定义返回代理的通用get()，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|417501|class+Proxy
{
++++My+const*+myOwner;
public:
++++Proxy(+My+const*+owner+)+:+myOwner(+owner+)+{}
++++operator+int()+const
++++{
++++++++return+myOwner->getInt();
++++}
++++operator+char()+const
++++{
++++++++return+myOwner->getChar();
++++}
};|code-block|syntax|javascript|417502|根据需要将其扩展到任意多个类型。|417503|entityMap^0|1W|7|24|6|2R|5|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

It's possible, but I'm not sure that it's a technique I'd recommend for
beginners. As in other cases, when you want the choice of functions to
depend on how the return value is used, you use a proxy; first define
functions like <code>getChar</code> and <code>getInt</code>, then a generic <code>get()</code> which
returns a Proxy like this: 

<pre><code>class Proxy
{
 My const* myOwner;
public:
 Proxy( My const* owner ) : myOwner( owner ) {}
 operator int() const
 {
 return myOwner-&gt;getInt();
 }
 operator char() const
 {
 return myOwner-&gt;getChar();
 }
};
</code></pre>

Extend it to as many types as you need.

blocks|key|417305|text|不，您不能通过返回类型重载；只能通过参数类型和常量/易失性限定符进行重载。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|417306|一种替代方法是使用引用参数“返回”：|417307|void+get(int,+int&);
void+get(int,+char&);|code-block|syntax|javascript|417308|虽然我可能会使用模板，或者像你的第二个例子一样使用不同名称的函数。|417309|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

No, you can't overload by return type; only by parameter types, and const/volatile qualifiers.

One alternative would be to "return" using a reference argument:

<pre><code>void get(int, int&amp;);
void get(int, char&amp;);
</code></pre>

although I would probably either use a template, or differently-named functions like your second example.

blocks|key|632621|text|你可以这样想：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|632622|您必须：|632623|++int+get(int);
++char+get(int);|code-block|syntax|javascript|632624|并且，在调用时不强制收集函数的返回值。|632625|现在，您可以调用|632626|++get(10);++->+there+is+an+ambiguity+here+which+function+to+invoke.+|632627|因此，如果根据返回类型允许重载，则没有意义。|632628|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|X|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

You can think this way:

You have:

<pre><code> int get(int);
 char get(int);
</code></pre>

And, it is not mandatory to collect the return value of the function while invoking. 

Now, You invoke

<pre><code> get(10); -&gt; there is an ambiguity here which function to invoke. 
</code></pre>

So, No meaning if overloading is allowed based on the return type.

blocks|key|417660|text|如前所述，模板在这种情况下有点过头了，但它仍然是一个值得一提的选项。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|417661|class+My+{
public:
++++template<typename+T>+T+get(int);
};

template<>+int+My::get<int>(int);
template<>+char+My::get<char>(int);|code-block|syntax|javascript|417662|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

As stated before, templates are overkill in this case, but it is still an option worth mentioning.

<pre><code>class My {
public:
 template&lt;typename T&gt; T get(int);
};

template&lt;&gt; int My::get&lt;int&gt;(int);
template&lt;&gt; char My::get&lt;char&gt;(int);
</code></pre>

blocks|key|417578|text|复活一个旧线程，但是我可以看到没有人提到ref限定符的重载。引用限定符是C%2B%2B11中添加的一种语言功能，我最近才偶然发现它-它没有像cv限定符那样广泛使用。主要思想是区分两种情况:当成员函数在右值对象上被调用时，以及在左值对象上被调用时。你基本上可以这样写(我稍微修改了一下OP的代码)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|417579|#include+<stdio.h>

class+My+{
public:
++++int+get(int)+&+{+//+notice+&
++++++++printf("returning+int..\n");
++++++++return+42;
++++}
++++char+get(int)+&&+{+//+notice+&&
++++++++printf("returning+char..\n");
++++++++return+'x';
++++};
};

int+main()+{
++++My+oh_my;
++++oh_my.get(13);+//+'oh_my'+is+an+lvalue
++++My().get(13);+//+'My()'+is+a+temporary,+i.e.+an+rvalue
}|code-block|syntax|javascript|417580|此代码将生成以下输出：|417581|returning+int..
returning+char..|417582|当然，就像cv限定符的情况一样，这两个函数可以返回相同的类型，并且重载仍然会成功。|417583|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Resurrecting an old thread, but I can see that nobody mentioned overloading by ref-qualifiers. Ref-qualifiers are a language feature added in C++11 and I only recently stumbled upon it - it's not so widespread as e.g. cv-qualifiers. The main idea is to distinguish between the two cases: when the member function is called on an rvalue object, and when is called on an lvalue object. You can basically write something like this (I am slightly modifying OP's code):

<pre><code>#include &lt;stdio.h&gt;

class My {
public:
 int get(int) &amp; { // notice &amp;
 printf("returning int..\n");
 return 42;
 }
 char get(int) &amp;&amp; { // notice &amp;&amp;
 printf("returning char..\n");
 return 'x';
 };
};

int main() {
 My oh_my;
 oh_my.get(13); // 'oh_my' is an lvalue
 My().get(13); // 'My()' is a temporary, i.e. an rvalue
}
</code></pre>

This code will produce the following output:

<pre><code>returning int..
returning char..
</code></pre>

Of course, as is the case with cv-qualifiers, both function could have returned the same type and overloading would still be successful.

blocks|key|632382|text|在C%2B%2B中无法通过返回类型进行重载。在不使用模板的情况下，最好使用get_int和get_char。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|632383|entityMap^0|X|7|15|8|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

There is no way to overload by return type in C++. Without using templates, using <code>get_int</code> and <code>get_char</code> will be the best you can do.

blocks|key|417386|text|你不能重载基于返回类型的方法。最好的方法是创建两个语法稍有不同的函数，比如在第二个代码片段中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|417387|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You can't overload methods based on return types. Your best bet is to create two functions with slightly different syntax, such as in your second code snippet.

blocks|key|632531|text|不能根据函数的返回类型重载函数。您可以根据此函数接受的参数的类型和数量进行超量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|632532|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

you can't overload a function based on the return type of the function. 
you can overlead based on the type and number of arguments that this function takes.

blocks|key|632709|text|我使用了James+Kanze的答案，并使用了一个代理：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|632710|https://stackoverflow.com/a/9569120/262458|offset|length|632711|我想避免在void*上使用大量丑陋的static_casts，所以我这样做了：|632712|#include+<SDL_joystick.h>
#include+<SDL_gamecontroller.h>

struct+JoyDev+{
++++private:
++++++++union+{
++++++++++++SDL_GameController*+dev_gc+=+nullptr;
++++++++++++SDL_Joystick*+++++++dev_js;
++++++++};
++++public:
++++++++operator+SDL_GameController*&()+{+return+dev_gc;+}
++++++++operator+SDL_Joystick*&()+++++++{+return+dev_js;+}

++++++++SDL_GameController*&+operator=(SDL_GameController*+p)+{+dev_gc+=+p;+return+dev_gc;+}
++++++++SDL_Joystick*&+++++++operator=(SDL_Joystick*+p)+++++++{+dev_js+=+p;+return+dev_js;+}
};

struct+JoyState+{
++++public:
++++++++JoyDev+dev;
};

int+main(int+argc,+char**+argv)
{
++++JoyState+js;

++++js.dev+=+SDL_JoystickOpen(0);

++++js.dev+=+SDL_GameControllerOpen(0);

++++SDL_GameControllerRumble(js.dev,+0xFFFF,+0xFFFF,+300);

++++return+0;
}|code-block|syntax|javascript|632713|完美的工作！|632714|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|16|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@]|9|@$D|X|E|Y|1|Z]]|A|$]]|$1|F|3|G|5|6|7|10|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|11|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|12|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|C]]]]

I used James Kanze's answer using a proxy:

<a href="https://stackoverflow.com/a/9569120/262458">https://stackoverflow.com/a/9569120/262458</a>

I wanted to avoid using lots of ugly static_casts on a void*, so I did this:

<pre class="lang-cpp prettyprint-override"><code>#include &lt;SDL_joystick.h&gt;
#include &lt;SDL_gamecontroller.h&gt;

struct JoyDev {
 private:
 union {
 SDL_GameController* dev_gc = nullptr;
 SDL_Joystick* dev_js;
 };
 public:
 operator SDL_GameController*&amp;() { return dev_gc; }
 operator SDL_Joystick*&amp;() { return dev_js; }

 SDL_GameController*&amp; operator=(SDL_GameController* p) { dev_gc = p; return dev_gc; }
 SDL_Joystick*&amp; operator=(SDL_Joystick* p) { dev_js = p; return dev_js; }
};

struct JoyState {
 public:
 JoyDev dev;
};

int main(int argc, char** argv)
{
 JoyState js;

 js.dev = SDL_JoystickOpen(0);

 js.dev = SDL_GameControllerOpen(0);

 SDL_GameControllerRumble(js.dev, 0xFFFF, 0xFFFF, 300);

 return 0;
}
</code></pre>

Works perfectly!

I read few questions here on SO about this topic which seems yet confusing to me. I've just begun to learn C++ and I haven't studied templates yet or operator overloading and such.

Now is there a simple way to overload

<pre><code>class My {
public:
 int get(int);
 char get(int);
}
</code></pre>

without templates or strange behavior? or should I just 

<pre><code>class My {
public:
 int get_int(int);
 char get_char(int);
}
</code></pre>

?

Overloading by return type

我在这里读到的关于这个话题的问题很少，这对我来说似乎仍然令人困惑。我刚刚开始学习C++，还没有学习过模板或者操作符重载之类的东西。现在有没有一种简单的重载方法？class My {public:    int get(int);    char get(int);}没有模板或奇怪的行为？或者我应该干脆class My {public:    int get_int(int);    char ge

问按返回类型重载
EN

回答 9

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问按返回类型重载EN

回答 9

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问按返回类型重载
EN