请教 std::vector<std::unique_ptr<B>>的类成员应该怎么写在构造函数 - V2EX
zxCoder
V2EX    C++

请教 std::vector<std::unique_ptr<B>>的类成员应该怎么写在构造函数

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  •   zxCoder Jun 14, 2021 2869 views
    This topic created in 1801 days ago, the information mentioned may be changed or developed.
    class A{ public: std::vector<int> a; std::vector<std::unique_ptr<B>> b; A(std::vector<int> a,std::vector<std::unique_ptr<B>> b); }; A::A(std::vector<int> a, std::vector<std::unique_ptr<B>> b):a(std::move(a)),b(std::move(b)) {} 

    这样写报错了

    8 replies    2021-06-16 07:07:52 +08:00
    zxCoder
        1
    zxCoder  
    OP
       Jun 14, 2021
    懂了 又是左值右值的问题。。。
    billwsy
        2
    billwsy  
       Jun 14, 2021 via iPhone
    这报了啥错?看着怎么没啥问题?
    kilasuelika
        3
    kilasuelika  
       Jun 15, 2021 via Android   1
    应该不是左值和右值的问题。
    unique_ptr 不能复制,但你用传值引用,就会发生复制,出错。
    kilasuelika
        4
    kilasuelika  
       Jun 15, 2021 via Android
    值传递
    zxCoder
        5
    zxCoder  
    OP
       Jun 15, 2021
    @billwsy
    @kilasuelika

    一开始 A a(x,y),报错了 改成 A a(x,std::move(y))就可以了
    shanPic
        6
    shanPic  
       Jun 15, 2021
    @zxCoder 如果楼主还是用的题目中的构造函数写法(传值形参),“ 改成 A a(x,std::move(y))就可以了”,我认为应该是触发了函数参数的 copy elision 。顺便问一下,是用的 c++17 或者 20 编的吗?
    zxCoder
        7
    zxCoder  
    OP
       Jun 15, 2021
    @shanPic c++14
    billwsy
        8
    billwsy  
       Jun 16, 2021 via iPhone
    @shanPic 是函数参数的 move ctor. 应该是 C++11 的语法
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