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ios - 条件绑定的初始化程序必须具有可选类型：不是“[AVCaptureDevice]”

问题描述

按照 repo 和教程：https ://github.com/brianadvent/CustomCamera

我收到以下代码错误：错误：

Initializer for conditional binding must have Optional type, not 'AVCaptureVideoPreviewLayer'

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

同样，对于以下部分

if let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) {
            self.previewLayer = previewLayer
            self.view.layer.addSublayer(self.previewLayer)
            self.previewLayer.frame = self.view.layer.frame
            captureSession.startRunning()

            let dataOutput = AVCaptureVideoDataOutput()
            dataOutput.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString):NSNumber(value:kCVPixelFormatType_32BGRA)] as [String : Any]

            dataOutput.alwaysDiscardsLateVideoFrames = true

            if captureSession.canAddOutput(dataOutput) {
                captureSession.addOutput(dataOutput)
            }

            captureSession.commitConfiguration()


            let queue = DispatchQueue(label: "com.brianadvent.captureQueue")
            dataOutput.setSampleBufferDelegate(self, queue: queue)



        }

与第二个代码片段相关的错误：条件绑定的初始化程序必须具有可选类型，而不是“AVCaptureVideoPreviewLayer”

标签： iosswiftiphone

解决方案

进行以下更改。

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

希望你明白这一点。

devices(an array) 不是可选的，也就是说，你肯定会得到这个数组。但是，devices.first是可选的，因为数组可能为空。

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