97 lines
1.6 KiB
C++
97 lines
1.6 KiB
C++
#include <iostream>
|
|
#include <mutex>
|
|
#include <fstream>
|
|
using namespace std;
|
|
|
|
enum class shape_type {
|
|
circle,
|
|
triangle,
|
|
rectangle,
|
|
};
|
|
|
|
|
|
class shape {
|
|
public:
|
|
shape() { cout << "shape" << endl; }
|
|
|
|
virtual void print() {
|
|
cout << "I am shape" << endl;
|
|
}
|
|
|
|
virtual ~shape() {}
|
|
};
|
|
|
|
class circle : public shape {
|
|
public:
|
|
circle() { cout << "circle" << endl; }
|
|
|
|
void print() {
|
|
cout << "I am circle" << endl;
|
|
}
|
|
};
|
|
|
|
class triangle : public shape {
|
|
public:
|
|
triangle() { cout << "triangle" << endl; }
|
|
|
|
void print() {
|
|
cout << "I am triangle" << endl;
|
|
}
|
|
};
|
|
|
|
class rectangle : public shape {
|
|
public:
|
|
rectangle() { cout << "rectangle" << endl; }
|
|
|
|
void print() {
|
|
cout << "I am rectangle" << endl;
|
|
}
|
|
};
|
|
|
|
// 利用多态 上转 如果返回值为shape,会存在对象切片问题。
|
|
shape *create_shape(shape_type type) {
|
|
switch (type) {
|
|
case shape_type::circle:
|
|
return new circle();
|
|
case shape_type::triangle:
|
|
return new triangle();
|
|
case shape_type::rectangle:
|
|
return new rectangle();
|
|
}
|
|
}
|
|
|
|
class shape_wrapper {
|
|
public:
|
|
explicit shape_wrapper(shape *ptr = nullptr) : ptr_(ptr) {}
|
|
|
|
~shape_wrapper() {
|
|
delete ptr_;
|
|
}
|
|
|
|
shape *get() const {
|
|
return ptr_;
|
|
}
|
|
|
|
private:
|
|
shape *ptr_;
|
|
};
|
|
|
|
|
|
void foo() {
|
|
shape_wrapper ptr(create_shape(shape_type::circle));
|
|
ptr.get()->print();
|
|
}
|
|
|
|
int main() {
|
|
|
|
// 第一种方式
|
|
shape *sp = create_shape(shape_type::circle);
|
|
sp->print();
|
|
delete sp;
|
|
|
|
// 第二种方式
|
|
foo();
|
|
|
|
return 0;
|
|
}
|