iOS 相册、麦克风和相机权限逻辑完善

因为相机是相册是日常开发中必不可少的功能，但是因为苹果的隐私政策，每次访问的时候都需要授权，没有授权app是无法访问相册和相机功能的，这样会造成app在用户第一次使用的时候出现一下显示不正常或者没有响应的感觉。
为了能提高用户的体验度，写一下相机相册简单的权限逻辑判断。
1、相册权限：
苹果文档中，相册权限状态有一下情况：
iOS 8.0+

API_AVAILABLE_BEGIN(macos(10.13), ios(8), tvos(10))
typedef NS_ENUM(NSInteger, PHAuthorizationStatus) {
    PHAuthorizationStatusNotDetermined = 0, // 用户没有选择User has not yet made a choice with regards to this application 
    PHAuthorizationStatusRestricted,        // 已拒绝This application is not authorized to access photo data. 
                                            // The user cannot change this application’s status, possibly due to active restrictions
                                            //   such as parental controls being in place.
    PHAuthorizationStatusDenied,            // 已拒绝User has explicitly denied this application access to photos data. 
    PHAuthorizationStatusAuthorized         //已同意授权 User has authorized this application to access photos data.  
};

通过一下方法判断是否继续下一步
需要导入#import <Photos/Photos.h>

PHAuthorizationStatus status = [PHPhotoLibrary authorizationStatus];
 if (status == PHAuthorizationStatusRestricted ||
                status == PHAuthorizationStatusDenied) 
{
                //无权限
          [SVProgressHUD showErrorWithStatus:@"Please set the Allow APP to access your photo album. Settings > Privacy > Album"];
   return ;
}
//第一次进来还没有选择是否授权
else if (status == PHAuthorizationStatusNotDetermined)
 {
                [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        if (status == PHAuthorizationStatusRestricted || status == PHAuthorizationStatusDenied)
                        {
                            // 用户拒绝，跳转到自定义提示页面
                            
                        }
                        else if (status == PHAuthorizationStatusAuthorized)
                        {
                            // 用户授权，弹出相册对话框
                            
                        }
                    });
                }];
                return;
}
else{
    // 用户授权，弹出相册对话框
}

2、相机
同相册一样，相机也是有对应的权限状态

typedef NS_ENUM(NSInteger, AVAuthorizationStatus) {
    AVAuthorizationStatusNotDetermined = 0,//没有选择
    AVAuthorizationStatusRestricted    = 1,//已拒绝
    AVAuthorizationStatusDenied        = 2,//已拒绝
    AVAuthorizationStatusAuthorized    = 3,//已授权
} API_AVAILABLE(macos(10.14), ios(7.0)) __WATCHOS_PROHIBITED __TVOS_PROHIBITED;

导入#import <AVFoundation/AVCaptureDevice.h>

AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
            if (authStatus == AVAuthorizationStatusRestricted || authStatus ==AVAuthorizationStatusDenied) {
                //无权限 
                
                return ;
            }
            else if (authStatus == AVAuthorizationStatusNotDetermined)
            {
                [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
                    if (!granted) {//不允许
                        
                    }else{//开启
                        
                    }
                }];
                return;
            }
else
{
  //已授权
}

获取麦克风权限逻辑和相机是差不多的只需把AVMediaTypeVideo 替换成AVMediaTypeAudio就可以了。
这就是目前相机、相册和麦克风的权限逻辑了，需要注意的一点是，这些方法大多是异步的，所以如果要在返回后做对应的操作，最好切换到主线程。