ios - swift + 火力地堡 : randomly picking a group of objects using a query to the server

Question

我正在使用 Swift 并使用 Firebase 作为后端为 iOS 构建一个测验应用程序。我希望能够进行一个查询，随机选择 10 个问题并返回它们。

Answer 1

首先，对于我的回答，您需要为每个问题赋予如下值:

    {
      "question1": {
        "question" : "Do you know swift",
        "answer" : "Nope",
        "value": 1
      },
      "question2": {
        "question" : "Do you know firebase",
        "answer" : "A bit",
        "value" : 2
      }
    }

之后，建议在您的 firebase 规则 ( firebase docs ) 中添加一个索引，如下所示:

    {
      "rules": {
        "questions": {
          ".indexOn": ["value"]
        }
      }
    }

接下来是快速的部分:

//Use a for loop to get 10 questions
for _ in 1...10{
  //generate a random number between 1 and the amount of questions you have
  var randomNumber = Int(arc4random_uniform(amountOfQuestions - 1)) + 1

  //The reference to your questions in firebase (this is an example from firebase itself)
  let ref = Firebase(url: "https://dinosaur-facts.firebaseio.com/dinosaurs")
    //Order the questions on their value and get the one that has the random value
  ref.queryOrderedByChild("value").queryEqualToValue(randomNumber)
    .observeEventType(.ChildAdded, withBlock: {
      snapshot in
        //Do something with the question
        println(snapshot.key)
    })
}

实际的 swift 代码可能存在缺陷，对于 firebase 特定代码，请查看 Ios documentation