iOS实现切换摄像头

前言（2018.3.1更新）

hihi 我来更新了，这边博客下面有个小哥哥说用了不好用，今天又有一位程序员朋友加我微信问这个问题，抽了5分钟做了个Demo在github上摄像头翻转，供大家参考，省的大家出现问题不知道怎么解决啦，嘻嘻。

以下原文：

//一定要导入这个库
#import <AVFoundation/AVFoundation.h>
//后面的session是指这个属性
@property (nonatomic,retain)AVCaptureSession *session;

// Switching between front and back cameras

- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position
{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices )
        if ( device.position == position )
            return device;
    return nil;
}

- (void)swapFrontAndBackCameras {
    // Assume the session is already running
    
    NSArray *inputs =self.session.inputs;
    for (AVCaptureDeviceInput *input in inputs ) {
        AVCaptureDevice *device = input.device;
        if ( [device hasMediaType:AVMediaTypeVideo] ) {
            AVCaptureDevicePosition position = device.position;
            AVCaptureDevice *newCamera =nil;
            AVCaptureDeviceInput *newInput =nil;
            
            if (position ==AVCaptureDevicePositionFront)
                newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
            else
                newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
            newInput = [AVCaptureDeviceInput deviceInputWithDevice:newCamera error:nil];
            
            // beginConfiguration ensures that pending changes are not applied immediately
            [self.session beginConfiguration];
            
            [self.session removeInput:input];
            [self.session addInput:newInput];
            
            // Changes take effect once the outermost commitConfiguration is invoked.
            [self.session commitConfiguration];
            break;
        }
    } 
}