Question

我试图创建专辑曲目，但我遇到了一个错误

这是我的路线代码

// Adding track to album
router.get('/:album_id/track/new', function(req, res){
    Album.findById(req.params.album_id, function(err, falbum){
        if(err){
            console.log(err);
        } else {
            res.render('tracks/add', {albums: falbum});
        }
    });
});

// Post routes
router.post('/:album_id/track',upload.single('songs'), function(req, res){
    Album.findById(req.params.album_id, function(err, album){
        if(err){
            console.log(err);
        } else {
            if(req.file){
                console.log('Uploading Song ....');
                var songs = req.file.filename;
            } else {
                console.log('No Song Uploaded...');
            }
            var songname = req.body.songname;
            var songs = songs;
            var newSong = {songname: songname, songs:songs};

            Track.create(newSong, function(err, track){
                if(err){
                    console.log(err);
                } else {
                    track.albumId.id = req.params.album_id;
                    track.save();
                    album.tracks.push(track);
                    album.save();
                    console.log('New Track is created');
                    res.redirect('/albums/' + album._id);
                }
            });
        }
    });
});

router.get('/:album_id',function(req, res){
    Album.findById(req.params.album_id).populate('tracks').exec(function(err, album){
        if(err){
            console.log(err);
        } else {
            res.render('albums/show', {albums: album})
        }
    });
});



module.exports = router;

我得到以下错误

v4\node_modules\mongoose\node_modules\mongodb\lib\utils.js:98
    process.nextTick(function() { throw err; });
                                  ^

TypeError: Cannot read property 'tracks' of null
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\routes\albums.js:53:11
    at Function.<anonymous> (C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\mongoose\lib\model.js:3324:16)
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\mongoose\lib\model.js:1870:14
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\async\lib\async.js:726:13
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\async\lib\async.js:52:16
    at done (C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\async\lib\async.js:246:17)
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\async\lib\async.js:44:16
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\async\lib\async.js:723:17
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\async\lib\async.js:167:37
    at model.callbackWrapper (C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\mongoose\lib\model.js:1843:11)
    at next_ (C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\hooks-fixed\hooks.js:89:34)
    at fnWrapper (C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\hooks-fixed\hooks.js:186:8)
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\mongoose\lib\model.js:3324:16
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\mongoose\lib\model.js:228:5
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\mongoose\lib\model.js:135:7
    at C:\Users\tjesu\Desktop\pidal\pidal-v4\node_modules\mongoose\node_modules\mongodb\lib\collection.js:504:5

我该怎么办？怎么样这个错误？我试图改变曲目跟踪但我仍然有错误谢谢！

Answer 1

您可以验证Album.findById是否会返回album？

您的数据库查询似乎与任何文档都不匹配，因此album未定义，因此您无法访问文档中的tracks属性。

Answer 2

我认为在成功创建pushing tracks之后，albums文档中的track出错了。

你应该推track._id而不是track。（因为我可以看到你试图挫败音轨，所以你必须在你的ObjectId和reference中使用schema）。

当您推送整个track document时，album可能无法成功保存。由于没有附加回调（album.save()），因此它没有显示实际的error。因此，当您使用album

时，不会创建null文档，并且会提供album.findById

这就是使用populate('tracks') 时显示此错误的原因： cannot read property tracks of null.

Track.create(newSong, function(err, track){
            if(err){
                console.log(err);
            } else {
                track.albumId.id = req.params.album_id;
                track.save();
                album.tracks.push(track._id);//Here _id should be pushed.
                album.save();
                console.log('New Track is created');
                res.redirect('/albums/' + album._id);
            }
        });

错误无法读取属性＆＃39; track＆＃39; of null（node.js）

2 个答案: