【More Effective C++】条款9：利用析构函数避免资源泄漏

思想：利用对象管理资源，用析构函数自动删除指针

• 避免资源泄漏
• 避免异常处理导致的代码编写困难，可执行文件变大的

class ALA {
public:
    virtual void processAdoption() = 0;
};

class Puppy: public ALA {
public:
    virtual void processAdoption() {
        std::cout << "Puppy\n";
    }
};

class Kitten: public ALA {
public:
    virtual void processAdoption() {
        std::cout << "Kitten\n";
    }
};

ALA* readALA(std::istream& s) {
    return new Puppy();
}

// void processAdoptions(std::istream& dataSource) {
//     while (dataSource) {
//         ALA *pa = readALA(dataSource);
//         pa->processAdoption();
//         delete pa;
//         break;
//     }
// }

// void processAdoptions(std::istream& dataSource) {
//     while (dataSource) {
//         ALA *pa = readALA(dataSource);
//         try { 
//             pa->processAdoption(); 
//         } catch(...) {
//             delete pa;
//             throw;
//         }
//         delete pa;
//         break;
//     }
// }

void processAdoptions(std::istream& dataSource) {
    while (dataSource) {
        std::unique_ptr<ALA> pa(readALA(dataSource));
        pa->processAdoption();
        break;
    }
}