class Member {
public:
Member(int idx) {
this->idx_ = idx;
}
int get_idx() {
return idx_;
}
void set_idx(int idx) {
this->idx_ = idx;
}
void foo();
private:
int idx_;
};
class SingletonClass {
public:
static SingletonClass& GetInstance() {
static SingletonClass inst;
return inst;
}
vector<Member*> get_members() {
return this->members_;
}
Member* get_member(int idx) {
return this->members_[idx];
}
void add_member(Member* mem) {
this->members_.push_back(mem);
}
private:
SingletonClass() {}
vector<Member*> members_;
};
void Member::foo() {
SingletonClass inst = SingletonClass::GetInstance();
cout << inst.get_members().size();
}
int main() {
SingletonClass inst = SingletonClass::GetInstance();
inst.add_member(new Member(0));
inst.add_member(new Member(1));
cout << inst.get_members().size() << endl;
Member* mem = inst.get_member(1);
mem->foo();
return 0;
}
输出为
2
0
看来,当我在Member::foo()
中获取SingletonClass的实例时,SingletonClass
的成员变量 vector members_
是已清除...任何人都可以向我解释为什么以及如何发生这种情况吗?我该如何修复它以获得预期结果?非常感谢!
最佳答案
It seems that when I get the instance of
SingletonClass
insideMember::foo()
, the member variable vectormembers_
ofSingletonClass
is cleared... Can anyone explain to me why and how this happen? And how can I fix it to get expected result?
您正在以下行中创建对象的拷贝:
SingletonClass inst = SingletonClass::GetInstance();
然后您正在修改拷贝的内容。原始对象保持不变。
用途:
SingletonClass& inst = SingletonClass::GetInstance();
为了防止这种情况在代码中的其他地方发生,请显式删除复制构造函数和复制赋值运算符。
private:
SingletonClass() {}
SingletonClass(SingletonClass const&) = delete;
SingletonClass& operator=(SingletonClass const&) = delete;
vector<Member*> members_;
关于c++ - 单例类的成员变量的生命周期是多少?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32146151/