EXEC_BAD_ACCESS错误，内存管理问题

Question

我读到这个错误来自内存管理问题，例如向已释放的对象发送消息。我在第二个“for”部分的第一行中的注释“输出有关“info”数组中歌曲的信息”之后收到错误。信息数组是否未存储我在第一个“for”部分中提供的对象？

还有其他想法吗？

MPMediaQuery *query = [[MPMediaQuery alloc] init]; //query iPod library
NSMutableArray *info; //create array to hold songs that fit
NSArray *allSongs = [query collections];

//only add those songs which have not
//been played since last login

for (MPMediaItem *recent in allSongs) {
    NSDate *lastPlayed = [recent valueForProperty:MPMediaItemPropertyLastPlayedDate];
    BOOL uploadInfo = [[PlayedSinceLastLogin alloc] initWithLastPlayedDateOfSong:lastPlayed] ;
    if (uploadInfo == YES) {
        [info addObject:recent];
    }
}

//output information about songs
//in the 'info' array

for (MPMediaItem *played in info) {
    NSString *playCount = [played valueForProperty:MPMediaItemPropertyPlayCount];
    NSString *lastPlayed = [played valueForProperty:MPMediaItemPropertyLastPlayedDate];
    NSString *songTitle =
    [played valueForProperty: MPMediaItemPropertyTitle];
    NSString *artistName =
    [played valueForProperty: MPMediaItemPropertyArtist];
    NSString *albumName =
    [played valueForProperty: MPMediaItemPropertyAlbumTitle];
    NSLog (@"\n %@ by %@, from album %@, played since last login.\nLast Played:%@.\nTotal Play Count: %@.", songTitle, artistName, albumName, lastPlayed,playCount);

}

Answer 1

看起来您实际上并没有为 info 创建一个 NSMutableArray 实例来指向，因此错误的访问错误可能是由于尝试处理一些随机的作为初始化对象的内存位。

更改

NSMutableArray *info;

为

NSMutableArray *info = [NSMutableArray array];