在同一范围C＆＃x2B;＆＃x2B上未申报的凹痕器
播放C ++ 20模块，我有以下片段：
export {
template<class T>
class Suite {
private:
std::vector<ConcreteBuilder<T>> things {};
};
template <class T>
class ConcreteBuilder : Builder<T> {
private:
// A collection of things of function pointers or functors
std::vector<std::function<void()>> things;
public:
// Virtual destructor
virtual ~TestBuilder() override {};
// Add a new thing to the collection of things
template<typename Function>
void add(Function&& fn) {
tests.push_back(std::forward<Function>(fn));
}
// override the build() base method from Builder<T>
virtual T build() const override {
return this->things;
}
};
}
而且我将获得此clang错误：
error: use of undeclared identifier 'ConcreteBuilder'
std::vector<ConcreteBuilder> things {};
为什么我无法访问在同一模块中的类型相同的水平？
Playing with C++ 20 modules, I have the following snippet:
export {
template<class T>
class Suite {
private:
std::vector<ConcreteBuilder<T>> things {};
};
template <class T>
class ConcreteBuilder : Builder<T> {
private:
// A collection of things of function pointers or functors
std::vector<std::function<void()>> things;
public:
// Virtual destructor
virtual ~TestBuilder() override {};
// Add a new thing to the collection of things
template<typename Function>
void add(Function&& fn) {
tests.push_back(std::forward<Function>(fn));
}
// override the build() base method from Builder<T>
virtual T build() const override {
return this->things;
}
};
}
And I am getting this Clang error:
error: use of undeclared identifier 'ConcreteBuilder'
std::vector<ConcreteBuilder> things {};
Why I can't access to a type that are in the same module at the same level?
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编译器从上到下来编译文件，而不是一次全部。它正在按照
std :: vector＆lt; concretebuilder＆lt; t＆gt;＆gt;的定义进行定义，然后才能获得类ConcreteBuilder的定义。因此，您需要在定义
ConcreteBuilder的定义之后移动suite的定义，因此编译器知道在向量定义中使用它时它是什么。The compiler compiles the file from the top down, not all at once. It is hitting the definition of
std::vector<ConcreteBuilder<T>>before it gets to the definition ofclass ConcreteBuilder.So, you need to move your definition of
Suiteafter the definition ofConcreteBuilder, so the compiler knows what it is when you use it in the vector definition.