使用 AngularFire 从 Firebase 中选择随机记录 [英] Pick random record from Firebase with AngularFire

问题描述

有没有办法像这样从 firebase 获取随机记录:

Is there any way to get random record from firebase like this:

{
  "-JbmopNnshefBT2nS2S7" : {
    "dislike" : 0,
    "like" : 0,
    "post" : "First post."
  },
  "-JbmoudijnJjDBSXNQ8_" : {
    "dislike" : 0,
    "like" : 0,
    "post" : "Second post."
  }
}

我用这段代码解决了这个问题，但它下载了所有记录，所以如果数据库更大，我的应用程序会运行得很慢:

I used this code to solve the problem, but it download all records, so if DB would be bigger, my app will work very slow:

HTML 代码:

    <div ng-controller="RandomCtrl">{{RandomPost.post}}</div>

JS代码:

var app=angular.module('App', ['firebase']);

app.controller('RandomCtrl', function($scope, $firebase){
    var ref = new Firebase("https://ind.firebaseio.com/");
    var sync=$firebase(ref);

    $scope.messages = sync.$asArray();

    $scope.GetRandomPost=function(){
        return $scope.RandomPost=$scope.messages[Math.floor(Math.random()*$scope.messages.length)];
    };

    $scope.GetRandomPost();    

});

推荐答案

您可以将 startAt 与您自己的增量索引一起使用.例如，假设您的记录中有索引(0 到 n).

You can use startAt with your own incremental index. For example, suppose you have index (0 to n) in your records.

做这个查询:orderByChild("index").startAt(rint).limitToFirst(1);

Do this query: orderByChild("index").startAt(rint).limitToFirst(1);

查看代码片段:

var rint = Math.floor((Math.random() * 10)) // you have 10 records
var query = ref.orderByChild("index").startAt(rint).limitToFirst(1);

var results = $firebaseArray(query);
results.$loaded(
  function(x) {
    // let's get one
    $scope.oneResult = x[0];
  }, function(error) {
    console.error("Error:", error);
  });
};

这篇关于使用 AngularFire 从 Firebase 中选择随机记录的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！