如何检测MPMediaItem是否代表iOS上受DRM保护的音轨

MPMediaItem* item;

NSURL* assetURL = [item valueForProperty:MPMediaItemPropertyAssetURL];
NSString *title=[item valueForProperty:MPMediaItemPropertyTitle];

if (!assetURL) {
    /*
     * !!!: When MPMediaItemPropertyAssetURL is nil, it typically means the file
     * in question is protected by DRM. (old m4p files)
     */
    NSLog(@"%@ has DRM",title);
}

MPMediaItem item;
NSURL *assetURL = [item valueForProperty:MPMediaItemPropertyAssetURL];
AVPlayerItem *avItem = [[AVPlayerItem alloc] initWithURL:assetURL];
BOOL fairplayed = avItem.asset.hasProtectedContent;

AVAsset

hasProtectedContent

NSURL *assetURL = [item valueForProperty:MPMediaItemPropertyAssetURL];
AVAsset *asset = [AVAsset assetWithURL:assetURL];

if ([asset hasProtectedContent] == NO) {..do your stuff..}

MPMediaItemPropertyAssetURL

AVPlayer

MPMediaItemPropertyAssetURL

MPMediaItemPropertyAssetURL

let itemUrl = targetMPMediaItem?.value(forProperty: MPMediaItemPropertyAssetURL) as? URL
if itemUrl != nil {
    let theAsset = AVAsset(url: itemUrl!)
    if theAsset.hasProtectedContent {
        //Asset is protected
        //Must be played only via MPPlayer
    } else {
        //Asset is not protected
        //Can be played both via AVPlayer & MPPlayer
    }
} else {
    //probably the asset is not avilable offline
    //Must be played only via MPPlayer
}

MPMediaItem

protectedAsset

if #available(iOS 9.2, *) {
    if (targetMPMediaItem?.hasProtectedAsset)! {
        //asset is protected
        //Must be played only via MPMusicPlayer
    } else {
        //asset is not protected
        //Can be played both via AVPlayer & MPMusicPlayer
    }
} else {
    //Fallback on earlier versions
    //Probably use the method explained earlier
}

-(void)checkDRMprotectionForItem:(MPMediaItem*)item OnCompletion:(void (^)(BOOL drmProtected))completionBlock
{
    dispatch_async(_drmCheckQueue, ^{
        BOOL drmStatus;
        NSURL* assetURL = [item valueForProperty:MPMediaItemPropertyAssetURL];
        if (!assetURL) {
            drmStatus = YES;
        }

        dispatch_async(dispatch_get_main_queue(), ^{
            if (completionBlock) {
                completionBlock(drmStatus);
            }
    });
    });
}

    let playerItem = AVPlayerItem(URL: mpMediaItem.assetURL!)
    playableByAVPlayer = (playerItem.status == .ReadyToPlay) ? true : false