iOS检测相机或者相册可用

#define OSVersionIsAtLeastiOS7   ([[UIDevice currentDevice].systemVersion floatValue]>=
7.0 ? YES:NO)  //定义的宏    
//检查相机是否可用
    if (OSVersionIsAtLeastiOS7) {
        NSString *mediaType =
AVMediaTypeVideo;
        AVAuthorizationStatus authStatus = [AVCaptureDevice
authorizationStatusForMediaType:mediaType];
        if (authStatus ==
AVAuthorizationStatusDenied) {
            
            UIAlertView *alertView =[[UIAlertView
alloc]initWithTitle:nil
message:@"请前往系统设置->隐私->相机，开启爱维宝贝权限"
delegate:nil
cancelButtonTitle:nil
otherButtonTitles:@"确定",
nil];
            [alertView show];
            return;
        }
    }
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    //检查相册是否可用
    if (OSVersionIsAtLeastiOS7) {
        ALAuthorizationStatus authStatus = [ALAssetsLibrary
authorizationStatus];
        if (authStatus ==
ALAuthorizationStatusDenied) {       
            UIAlertView *alertView =[[UIAlertView
alloc]initWithTitle:nil
message:@"请前往系统设置->隐私->相片，开启爱维宝贝权限"
delegate:nil
cancelButtonTitle:nil
otherButtonTitles:@"确定",
nil];
            [alertView show];
            return;
        }
        
    }