c++14通过字符串动态实例化

duqn

文件架构:


animal.h

1. #ifndef ANIMAL_H
   
2. #define ANIMAL_H
   
3. 
   
4. #include <iostream>
   
5. 
   
6. class Animal {
   
7. public:
   
8.     virtual void speak() = 0;
   
9.     virtual ~Animal() {}
   
10. };
    
11. 
    
12. #endif // ANIMAL_H
    

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animal_factory.h

1. #ifndef ANIMAL_FACTORY_H
   
2. #define ANIMAL_FACTORY_H
   
3. 
   
4. #include "animal.h"
   
5. #include <memory>
   
6. #include <string>
   
7. #include <unordered_map>
   
8. #include <functional>
   
9. 
   
10. class AnimalFactory {
    
11. public:
    
12.     using CreateFunc = std::function<std::unique_ptr<Animal>()>;
    
13. 
    
14.     static void registerAnimal(const std::string& name, CreateFunc func);
    
15.     static std::unique_ptr<Animal> createAnimal(const std::string& name);
    
16. 
    
17. private:
    
18.     // 将getRegistry声明为一个私有的静态成员函数
    
19.     static std::unordered_map<std::string, CreateFunc>& getRegistry();
    
20. };
    
21. 
    
22. template<typename T>
    
23. struct Registrator {
    
24.     Registrator(const std::string& name) {
    
25.         AnimalFactory::registerAnimal(name, &T::create);
    
26.     }
    
27. };
    
28. 
    
29. #endif // ANIMAL_FACTORY_H
    

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animal_factory.cpp

1. #include "animal_factory.h"
   
2. #include "cat.h"
   
3. #include "dog.h"
   
4. 
   
5. void AnimalFactory::registerAnimal(const std::string& name, CreateFunc func) {
   
6.     getRegistry()[name] = func;
   
7. }
   
8. 
   
9. std::unique_ptr<Animal> AnimalFactory::createAnimal(const std::string& name) {
   
10.     const auto& reg = getRegistry();
    
11.     auto it = reg.find(name);
    
12.     if (it != reg.end()) {
    
13.         return it->second();
    
14.     }
    
15.     return nullptr;
    
16. }
    
17. 
    
18. // 定义getRegistry，以满足之前的声明
    
19. std::unordered_map<std::string, AnimalFactory::CreateFunc>& AnimalFactory::getRegistry() {
    
20.     static std::unordered_map<std::string, CreateFunc> instance;
    
21.     return instance;
    
22. }
    

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cat.h

1. #ifndef CAT_H
   
2. #define CAT_H
   
3. 
   
4. #include "animal.h"
   
5. #include <memory>
   
6. 
   
7. class Cat : public Animal {
   
8. public:
   
9.     void speak() override;
   
10.     static std::unique_ptr<Animal> create();
    
11. };
    
12. 
    
13. #endif // CAT_H
    

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cat.cpp

1. #include "animal_factory.h"
   
2. #include "cat.h"
   
3. 
   
4. void Cat::speak() {
   
5.     std::cout << "Meow" << std::endl;
   
6. }
   
7. 
   
8. std::unique_ptr<Animal> Cat::create() {
   
9.     return std::make_unique<Cat>();
   
10. }
    
11. 
    
12. static Registrator<Cat> reg_cat("cat");

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dog.h

1. #ifndef DOG_H
   
2. #define DOG_H
   
3. 
   
4. #include "animal.h"
   
5. #include <memory>
   
6. 
   
7. class Dog : public Animal {
   
8. public:
   
9.     void speak() override;
   
10.     static std::unique_ptr<Animal> create();
    
11. };
    
12. 
    
13. #endif // DOG_H
    

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dog.cpp

1. #include "animal_factory.h"
   
2. #include "dog.h"
   
3. 
   
4. void Dog::speak() {
   
5.     std::cout << "Woof" << std::endl;
   
6. }
   
7. 
   
8. std::unique_ptr<Animal> Dog::create() {
   
9.     return std::make_unique<Dog>();
   
10. }
    
11. 
    
12. static Registrator<Dog> reg_dog("dog");

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main.cpp

1. #include "animal_factory.h"
   
2. #include <iostream>
   
3. 
   
4. int main() {
   
5.     auto cat = AnimalFactory::createAnimal("cat");
   
6.     if (cat) cat->speak();
   
7. 
   
8.     auto dog = AnimalFactory::createAnimal("dog");
   
9.     if (dog) dog->speak();
   
10. 
    
11.     return 0;
    
12. }
    

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duqn

编译命令：

1. g++ -std=c++14 -o animal_app animal_factory.cpp cat.cpp dog.cpp main.cpp

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效果：

1. root@iZ8vb21cs5hzwls5h5s2hbZ:/cpp/240326# g++ -std=c++14 -o animal_app animal_factory.cpp cat.cpp dog.cpp main.cpp
   
2. root@iZ8vb21cs5hzwls5h5s2hbZ:/cpp/240326# ./animal_app
   
3. Meow
   
4. Woof
   
5. root@iZ8vb21cs5hzwls5h5s2hbZ:/cpp/240326#
   

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duqn

Makefile:

1. CXX = g++
   
2. CXXFLAGS = -std=c++14 -Wall
   
3. LDFLAGS =
   
4. OBJFILES = animal_factory.o cat.o dog.o main.o
   
5. TARGET = animal_app
   
6. 
   
7. all: $(TARGET)
   
8. 
   
9. $(TARGET): $(OBJFILES)
   
10.         $(CXX) $(LDFLAGS) -o $(TARGET) $(OBJFILES)
    
11. 
    
12. %.o: %.cpp
    
13.         $(CXX) $(CXXFLAGS) -c $<
    
14. 
    
15. clean:
    
16.         rm -f $(OBJFILES) $(TARGET)
    

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