public member function
<future>
bool valid() const noexcept;
Check for valid shared state
Return value
true
if the object is associated with a shared state.
false
otherwise.
Example
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// future::valid
#include <iostream> // std::cout
#include <future> // std::async, std::future
#include <utility> // std::move
int get_value() { return 10; }
int main ()
{
std::future<int> foo,bar;
foo = std::async (get_value);
bar = std::move(foo);
if (foo.valid())
std::cout << "foo's value: " << foo.get() << '\n';
else
std::cout << "foo is not valid\n";
if (bar.valid())
std::cout << "bar's value: " << bar.get() << '\n';
else
std::cout << "bar is not valid\n";
return 0;
}
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Output:
foo is not valid
bar's value: 10
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Data races
The future object is accessed.
Exception safety
No-throw guarantee: never throws exceptions.