Swift&Firebase | 检查用户是否存在用户名

Question

我正在尝试允许用户通过搜索用户名来启动游戏并关注其他用户.我需要能够确保具有该用户名的用户存在.我正在使用以下代码但是虽然它if被调用但是else它应该被调用.

let checkWaitingRef = Firebase(url:"https://test.firebaseio.com/users")
checkWaitingRef.queryOrderedByChild("username").queryEqualToValue("\(username!)")
            .observeEventType(.ChildAdded, withBlock: { snapshot in

    if snapshot.value.valueForKey("username")! as! String == username! {

    } else {

    }

JSON数据树

{
    "097ca4a4-563f-4867ghj0-6209288bd7f02" : {
        "email" : "test1@tes1.com",
        "uid" : "097ca4a4-563f-4867ghj0-6209288bd7f02",
        "username" : "test1",
        "waiting" : "0"
    },
    "55a8f979-ad0d-438u989u69-aa4a-45adb16175e7" : {
        "email" : "test2@test2.com",
        "uid" : "55a8f979-ad0d-438u989u69-aa4a-45adb16175e7",
        "username" : "test2",
        "waiting" : "0"
    }
}

Answer 1

轻松修复:

不要使用.childAdded,因为当查询找不到任何内容时,块将不会执行.

而是使用.Value并检查NSNull

    let checkWaitingRef = Firebase(url:"https://test.firebaseio.com/users")
    checkWaitingRef.queryOrderedByChild("username").queryEqualToValue("\(username!)")
                .observeEventType(.Value, withBlock: { snapshot in

            if ( snapshot.value is NSNull ) {
                print("not found)")

            } else {
                print(snapshot.value)
            }
     })