在非模板类中强制模板方法 [英] Force template method in non-template class

问题描述

我尝试实现此类的以下行为/语法/用法：

I try to achieve the following behavior/syntax/usage of this class:

Data1 dataType1;
Data2 dataType2;

int intType;
float floatType;

dataType1.method( intType );
dataType1.method( floatType );

dataType2.method( intType );
dataType2.method( floatType );

我的方法是：

struct CDataBase
{
    template< typename T > virtual void method( T type ) = 0;
};

struct CData1 : CDataBase
{
    template< typename T > void method( T type ) {}
};

struct CData2 : CDataBase
{
    template< typename T > void method( T type ) {}
};

但是虚拟模板方法是不可能的。也不需要一个实际的基类，但我必须确保一些类得到一个（模板）'method（）'实现。

However virtual template methods aren't possible. Also there is no need for an actual base class, However I have to ensure that some classes got a (template) 'method()' implemented.

如何强制一个非模板化的类/结构来覆盖模板方法？

How do I force a non-templated class/struct to override a template method?

编辑：
这是我的实际布局：

This is my actual layout:

struct Data0
{
    int someVar;

    template< class T >
    void decode( T& type )
    {
        type.set( someVar );
    }
};

编辑：
在当前版本的C ++（11）behavoir我试图实现是不可能的。除此之外，我应该重新编码这部分，以避免这个问题。

in the current version of C++ (11) the behavoir I try to achieve isn't possible. In addition to that, I should really recode this part to avoid this problem. However I accept the only answer given, thanks for you affort.

推荐答案

检查特定函数实现的基本思想是什么？模板参数类型，是尝试实例化这些的函数指针。如果函数指针初始化无法解决，编译器会报错。

The basic idea to check for specific functions implemented of a given template parameter type, is to try instantiate function pointers of these. The compiler will complain, if the function pointer initializations cannot be resolved.

下面是一些示例代码来说明原理：

Here's some sample code to illustrate the principle:

template<typename T>
void check_has_foo_function() {
    void (T::*check)(int, double) = &T::foo;
    (void)check;
}

struct A {
    void foo(int, double) {};
};

struct B {
    void bar(int, double) {};
};

template<typename CheckedClass>
struct Client {
    void doSomething() {
        check_has_foo_function<CheckedClass>();
        CheckedClass x;
        x.foo(5,3.1415);
    }
};

int main() {

    Client<A> clientA;
    clientA.doSomething();

    // Uncomment the following lines to see the compilation fails
    // Client<B> clientB;
    // clientB.doSomething();
    return 0;
}

注意调用 check_has_foo_function< CheckedClass> ）; 函数将被完全优化，并且对运行时性能没有任何影响。

Note the call to the check_has_foo_function<CheckedClass>(); function will be completely optimized out, and doesn't have any impact on runtime performance.

（例如使用预处理器宏生成检查）。我已在GitHub上发布了使用这些技术的小实验框架。

Based upon this, further abstractions could be provided (e.g. to generate checks using preprocessor macros). I have published a little experimental framework on GitHub that uses these techniques.

这篇关于在非模板类中强制模板方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！