問題描述

template<>
class A{
//some class data
};

這種代碼我見過很多次了.上面代碼中template<>的作用是什么?在哪些情況下我們需要強制使用它?

I have seen this kind of code many times. what is the use of template<> in the above code? And what are the cases where we need mandate the use of it?

推薦答案

template<> 告訴編譯器遵循模板特化，特別是完全特化.通常，class A 應該是這樣的:

template<> tells the compiler that a template specialization follows, specifically a full specialization. Normally, class A would have to look something like this:

template<class T>
class A{
  // general implementation
};

template<>
class A<int>{
  // special implementation for ints
};

現在，每當使用 A 時，都會使用專用版本.你也可以用它來專門化函數:

Now, whenever A<int> is used, the specialized version is used. You can also use it to specialize functions:

template<class T>
void foo(T t){
  // general
}

template<>
void foo<int>(int i){
  // for ints
}

// doesn't actually need the <int>
// as the specialization can be deduced from the parameter type
template<>
void foo(int i){
  // also valid
}

通常情況下，你不應該專門化函數，因為簡單的重載通常被認為是優越的:

Normally though, you shouldn't specialize functions, as simple overloads are generally considered superior:

void foo(int i){
  // better
}

<小時>

現在，為了讓它顯得矯枉過正，以下是一個部分專業化:

template<class T1, class T2>
class B{
};

template<class T1>
class B<T1, int>{
};

與完全特化的工作方式相同，只是當第二個模板參數是 int(例如，B、B 等).

Works the same way as a full specialization, just that the specialized version is used whenever the second template parameter is an int (e.g., B<bool,int>, B<YourType,int>, etc).

這篇關于模板是什么意思?在 C++ 中使用空尖括號?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！