对mongoDb游标进行排序

Question

I'm having difficulties finding the right syntax for my sorted cursor.

What it needs to do is return a sorted cursor which I can then iterate after each item is processed.

Here's my function which works perfectly without the sort, but returns nothing once sort() added (I strongly suspect a syntax issue but can't seem to find the right doc):

db.collection('products').find({}).sort({rnd: 1},function(err, cursor){
    console.log(found);
    if(err){
        console.log(err);
    }
    function processItem(err, item) {
        if(err){
            console.log(err);
        }
        if(item === null) {
            console.log('cursor exhausted');
            db.close();
        }else{
            someAsyncOperation(item,function(){
                cursor.nextObject(processItem);
            });
        }
    }
    cursor.nextObject(processItem);
});

Answer 1

I was making a wrong assumption about the syntax. The cursor returned by find() needs to be sorted, then iterated like so :

var cursor = db.collection('products4Scrape').find({}).sort({rnd: 1});
iterateCursor();

function iterateCursor(){
    if(err){
        console.log(err);
    }
    function processItem(err, item) {
        if(err){
            console.log(err);
        }
        if(item === null) {
            console.log('cursor exhausted');
            db.close();
        }else{
            someAsyncOperation(item,function(){
                cursor.nextObject(processItem);
            });
        }
    }
    cursor.nextObject(processItem);
}