查询和 Firebase 中的位置（swift 3）

Question

如何在 firebase 中进行查询？在 oracle sql 上，查询将是

"select * from users where username = "SomeUser"

我需要在 Firebase、Swift 3 中做同样的事情

Answer 1

您需要使用queryOrderedByChild 和queryStartingAtValue。这应该可以让您朝着正确的方向开始。

queryStartingAtValue(username).queryEndingAtValue(username)

let username = "SomeUser"

FIRDatabase.database().reference.child("users").queryOrderedByChild("username").queryStartingAtValue(username).queryEndingAtValue(username).observeEventType(.ChildAdded, withBlock: { (snapshot) -> Void in

}

queryEqual(toValue: 用户名)

let searchRef = FIRDatabase.database().reference().child("users").queryOrdered(byChild: "username").queryEqual(toValue: username)

Answer 2

Swift 3 && Firebase 3

我希望这能帮助你理解。来了

这是数据结构的示例：

这里是代码：

    let username = "DavidMouse"

    // create searchRef or queryRef you name it
    let searchRef = FIRDatabase.database().reference().child("users").queryOrdered(byChild: "username").queryEqual(toValue: username)

    // search the username
    searchRef.observeSingleEvent(of: .value, with: { (snapshot) in

        guard snapshot.value is NSNull else {

            // yes we got the user
            let user = snapshot.value as! String
            print("\(user) is exists")
            return
        }

        // no there is no user with desire username
        print("\(username) is exists")
    }) { (error) in
        print("Failed to get snapshot", error.localizedDescription)
    }