如何添加 $q 来命令执行？

Question

我需要下令执行。我需要确保我的 COMPLETE coords() 方法在被调用后完成。如何向它添加一个承诺或 $q ？我尝试在控制台上打印，发现 coords 中的 forEach 循环在执行 coords() 函数的最后一行后完成。请参阅下面的代码。我对角度帮助真的很陌生

var appa = angular.module('appa',['firebase','uiGmapgoogle-maps']);
appa.controller('mainCtrl', function($firebaseObject,$scope,$q) {

              $scope.coords = function(){
               
                var ref =  firebase.database().ref();
                var latArray = [];
                var lngArray = [];
                var cenlat;
                var cenlng;
                  var marker = [];
                ref.once("value")
                .then(function(snapshot)
                {
                snapshot.forEach(function(child)
                {

                  latArray.push(child.child("Lat").val());
                  console.log(child.child("Lat").val());
                  lngArray.push(child.child("Long").val());
                  var mark = {
                  id: child.child("Id").val(),
                  coords: {
                  latitude: child.child("Lat").val(),
                  longitude: child.child("Long").val()
                  },
                  options: { title: child.child("Alt").val() }
                  };
                  marker.push(mark);
CONSOLE.LOG("wWHY IS THIS PRINTED aFTER??? AND HOW TO HANDLE THIS ??");
                });

                   cenlat = (Math.max.apply(Math,latArray)+Math.min.apply(Math,latArray)/2);
                   cenlng = (Math.max.apply(Math,lngArray)+Math.min.apply(Math,lngArray)/2);

                });
                $scope.map.center.latitude = cenlat;
                $scope.map.center.longitude = cenlng;
CONSOLE.LOG("wWHY IS THIS PRINTED BEFORE??? AND HOW TO HANDLE THIS ??");
});
                };

              $scope.map = {
                center:
                {
                  latitude: 51,
                  longitude: 4
                         },
                 zoom: 2
                      };

      $scope.coords();
      


   });

Answer 1

您正在使用 firebase 并且可以轻松地检查返回的子节点，并将它们存储在一个变量中。然后在 forEach 循环中递减变量。

//initialized var a, is having child count
a = snapshot.numChildren();

下面的完整代码将创建有序执行，并有一个基本的 Promise 实现。我还添加了 console.log 来显示订单。希望对您有所帮助。

//complete code

var appa = angular.module('appa',['firebase','uiGmapgoogle-maps']);
appa.controller('mainCtrl', function($firebaseObject,$scope,$q){

              $scope.coords = function(){
var q = $q.defer();
                var ref =  firebase.database().ref();
                var latArray = [];
                var lngArray = [];
                var cenlat;
                var cenlng;
                var a="0";
                var marker = [];

                ref.once("value")
                .then(function(snapshot)
                {
               a = snapshot.numChildren();
                console.log(a);
                snapshot.forEach(function(child)
                {
                  latArray.push(child.child("Lat").val());
                  console.log(child.child("Lat").val());
                  lngArray.push(child.child("Long").val());
                  var mark = {
                  id: child.child("Id").val(),
                  coords: {
                  latitude: child.child("Lat").val(),
                  longitude: child.child("Long").val()
                  },
                  options: { title: child.child("Alt").val() }
                  };
                  a= a-1;
                  console.log("this is current"+a);
                  marker.push(mark);
                });
console.log("hi"+a);
console.log("going for cenlat"+cenlat);
            cenlat = (Math.max.apply(Math,latArray)+Math.min.apply(Math,latArray)/2);
console.log("done with cenlat"+cenlat);
console.log("going for cenlng"+cenlng);
            cenlng = (Math.max.apply(Math,lngArray)+Math.min.apply(Math,lngArray)/2);
console.log("done with cenlng"+cenlng);
            $scope.map.center.latitude = cenlat;
            $scope.map.center.longitude = cenlng;
            if(a==0){
            q.resolve('resolved');
            }
            else{
            q.reject('rejected');
            }
                });

                };
              $scope.map = {
                center:
                {
                  latitude: 51,
                  longitude: 4
                         },
                 zoom: 2
                      };

    $scope.coords().then(
        function(v){
console.log(v);
      },
    function(err){
console.log(err);
    });

   });