1.7 构造函数-初始化列表¶

初始化列表并没有效率上的优势，仅为了书写方便
初始化列表的顺序只跟声明顺序相关，使用初始化列表时请根据声明顺序初始化！！！

class T {
  public:
    T (): b_(10), a_(b_) {
        std::cout << a_ << "," << b_ << endl;
    }
    T (const int t ): b_(t), a_(b_) {
        std::cout << a_ << "," << b_ << endl;
    }
  private:
    int a_;
    int b_;
};

int main() {
    T t, t1(100);
    return 0;
}

/*
 结果
-858993460,10
-858993460,100
*/