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std::future::valid

STD：：未来：：有效

bool valid() const;​(since C++11)

检查未来是否指共享状态。

这种情况仅适用于未违约的期货，即未被构造或从%28i.e移出的期货。归还std::promise::get_future()，，，std::packaged_task::get_future()或std::async()%29，直到第一次get()或share()叫做。

如果除析构函数、移动赋值运算符或valid调用future这不引用共享状态%28，尽管鼓励实现抛出std::future_error指示no_state在本例中%29。从其未来对象中移动是有效的valid()是false...

参数

%280%29

返回值

true如果%2A这指的是共享状态，否则为false...

例外

noexcept规格：

noexcept

例

另见

waitwaits for the result to become available (public member function)

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