var query:PFQuery=PFQuery(className: "User");
    query.findObjectsInBackgroundWithBlock {
        (objects: [AnyObject]!,error: NSError!) -> Void in
        if !(error != nil) {
            for(var i=0;i<objects.count;i++){
                var object=objects[i] as PFObject;
                var name = object.objectForKey("username") as String;
                println(name);

            }
        }
    }

我试过更换

var query:PFQuery=PFQuery(className: "User");

同

var query:PFQuery=PFQuery(className: "AnotherClass");

一切都像我应该的那样奏效.我认为对于“用户”类来说一定是特别的