如何设置表示接口的类?这只是一个抽象基类吗?
当前回答
如果您只需要接口的静态绑定(没有虚拟的,没有接口类型本身的实例,接口仅作为指南):
#include <iostream>
#include <string>
// Static binding interface
// Notice: instantiation of this interface should be usefuless and forbidden.
class IBase {
protected:
IBase() = default;
~IBase() = default;
public:
// Methods that must be implemented by the derived class
void behaviorA();
void behaviorB();
void behaviorC() {
std::cout << "This is an interface default implementation of bC().\n";
};
};
class CCom : public IBase {
std::string name_;
public:
void behaviorA() { std::cout << "CCom bA called.\n"; };
};
class CDept : public IBase {
int ele_;
public:
void behaviorB() { std::cout << "CDept bB called.\n"; };
void behaviorC() {
// Overwrite the interface default implementation
std::cout << "CDept bC called.\n";
IBase::behaviorC();
};
};
int main(void) {
// Forbid the instantiation of the interface type itself.
// GCC error: ‘constexpr IBase::IBase()’ is protected within this context
// IBase o;
CCom acom;
// If you want to use these interface methods, you need to implement them in
// your derived class. This is controled by the interface definition.
acom.behaviorA();
// ld: undefined reference to `IBase::behaviorB()'
// acom.behaviorB();
acom.behaviorC();
CDept adept;
// adept.behaviorA();
adept.behaviorB();
adept.behaviorC();
// adept.IBase::behaviorC();
}
其他回答
如果您只需要接口的静态绑定(没有虚拟的,没有接口类型本身的实例,接口仅作为指南):
#include <iostream>
#include <string>
// Static binding interface
// Notice: instantiation of this interface should be usefuless and forbidden.
class IBase {
protected:
IBase() = default;
~IBase() = default;
public:
// Methods that must be implemented by the derived class
void behaviorA();
void behaviorB();
void behaviorC() {
std::cout << "This is an interface default implementation of bC().\n";
};
};
class CCom : public IBase {
std::string name_;
public:
void behaviorA() { std::cout << "CCom bA called.\n"; };
};
class CDept : public IBase {
int ele_;
public:
void behaviorB() { std::cout << "CDept bB called.\n"; };
void behaviorC() {
// Overwrite the interface default implementation
std::cout << "CDept bC called.\n";
IBase::behaviorC();
};
};
int main(void) {
// Forbid the instantiation of the interface type itself.
// GCC error: ‘constexpr IBase::IBase()’ is protected within this context
// IBase o;
CCom acom;
// If you want to use these interface methods, you need to implement them in
// your derived class. This is controled by the interface definition.
acom.behaviorA();
// ld: undefined reference to `IBase::behaviorB()'
// acom.behaviorB();
acom.behaviorC();
CDept adept;
// adept.behaviorA();
adept.behaviorB();
adept.behaviorC();
// adept.IBase::behaviorC();
}
除了上面写的内容,还有一点补充:
首先,确保析构函数也是纯虚拟的
第二,您可能希望在执行时实际上继承(而不是正常继承),只是为了获得好的度量。
在C++20中,可以使用概念而不是类。它比继承更有效率。
template <class T>
concept MyInterface = requires (T t) {
{ t.interfaceMethod() };
};
class Implementation {
public:
void interfaceMethod();
};
static_assert(MyInterface<Implementation>);
然后您可以在函数中使用它:
void myFunction(MyInterface auto& arg);
限制是不能在容器中使用它。
就我所能测试的而言,添加虚拟析构函数非常重要。我使用的是用new创建的对象,用delete销毁的对象。
如果不在接口中添加虚拟析构函数,则不会调用继承类的析构函数。
class IBase {
public:
virtual ~IBase() {}; // destructor, use it to call destructor of the inherit classes
virtual void Describe() = 0; // pure virtual method
};
class Tester : public IBase {
public:
Tester(std::string name);
virtual ~Tester();
virtual void Describe();
private:
std::string privatename;
};
Tester::Tester(std::string name) {
std::cout << "Tester constructor" << std::endl;
this->privatename = name;
}
Tester::~Tester() {
std::cout << "Tester destructor" << std::endl;
}
void Tester::Describe() {
std::cout << "I'm Tester [" << this->privatename << "]" << std::endl;
}
void descriptor(IBase * obj) {
obj->Describe();
}
int main(int argc, char** argv) {
std::cout << std::endl << "Tester Testing..." << std::endl;
Tester * obj1 = new Tester("Declared with Tester");
descriptor(obj1);
delete obj1;
std::cout << std::endl << "IBase Testing..." << std::endl;
IBase * obj2 = new Tester("Declared with IBase");
descriptor(obj2);
delete obj2;
// this is a bad usage of the object since it is created with "new" but there are no "delete"
std::cout << std::endl << "Tester not defined..." << std::endl;
descriptor(new Tester("Not defined"));
return 0;
}
如果在没有virtual~IBase(){};的情况下运行前面的代码;,您将看到从未调用析构函数Tester::~Tester()。
我还是C++开发的新手。我从Visual Studio(VS)开始。
然而,似乎没有人提到VS(.NET)中的__interface。我不太确定这是否是声明接口的好方法。但它似乎提供了额外的强制执行(文件中提到)。这样就不必显式指定虚拟TYPE Method()=0;,因为它将被自动转换。
__interface IMyInterface {
HRESULT CommitX();
HRESULT get_X(BSTR* pbstrName);
};
然而,我不使用它,因为我担心跨平台编译兼容性,因为它只在.NET下可用。
如果有人对此感兴趣,请分享。:-)
谢谢