c++ - 类模板中封闭类型的静态数组

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What is an undefined reference/unresolved external symbol error and how do I fix it?
                                
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我正在尝试编译以下内容：

template<typename T>
class Foo {
protected:
   static Foo<T>* pool[5];
public:
   static Foo* Bar() {
      pool[1] = new Foo();
   }
};

int main() {
   Foo<int>* b = new Foo<int>();
   b->Bar();
}

我得到错误：

 undefined reference to `Foo<int>::pool'

我如何导致定义池阵列？

最佳答案

您可以像这样在类之外定义模板化类的静态成员。

// for generic T
template<typename T>
Foo<T>* Foo<T>::pool[5] = {0, 0, 0, 0, 0};

// specifically for int
template<>
Foo<int>* Foo<int>::pool[5] = {0, 0, 0, 0, 0};