用于条件绑定(bind)的 Swift 初始化程序必须具有可选类型，而不是 '[AVCaptureDevice]'

Question

我的 swift 项目中有以下代码

if let availabeDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInMicrophone,
.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back).devices {

            captureDevice = availabeDevices.first
        }

当我运行此代码时，它在 if 行上给出一个错误，内容如下:

Initializer for conditional binding must have Optional type, not '[AVCaptureDevice]'

我尝试在 .devices 之后添加 ?，但出现以下错误:

Cannot use optional chaining on non-optional value of type '[AVCaptureDevice]'

我该怎么办？

Answer 1

使用下面的行。

if let captureDevice = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInMicrophone, .builtInWideAngleCamera], 
mediaType: AVMediaType.video, 
position: .back).devices.first {
            self.captureDevice = captureDevice
        }