带有 DISPATCH_TIME_FOREVER 的 swift 4.0 dispatch_semaphore_wait

Question

dispatch_semaphore_wait(writeSemaphore!, DISPATCH_TIME_FOREVER) 

给出 DISPATCH_TIME_FOREVER 的错误，即

Cannot convert value of type 'Int' to expected argument type 'dispatch_time_t' (aka 'UInt64') 

Een 分配一个值 DispatchTime.distantFuture 无济于事。

谁能告诉我dispatch_time_t(超时)的值是多少

Answer 1

我会去:

    writeSemaphore!.wait(timeout: .distantFuture)

但是你应该通过确保你的可选值不为零来改进你的代码。去找守卫如下:

    guard let writeSemaphore = writeSemaphore else { return }

    writeSemaphore.wait(timeout: .distantFuture)