在循环中无法获得总和 [英] Can't get the summation in for loop

问题描述

在 for循环中有一个角度服务，它返回一个对象数组。我想获得由 service 返回的值的总和，但是我最终没有得到任何结果。我的服务工作正常，但我的问题是我无法得到总结。下面是我的代码

控制器

  var TotalOBValueLand = 0; （var i = 0; i <$ scope.selectedProp.length; i ++）{
 AccountService.getTopAccountDetails（$ scope.selectedProp [i] [propId]）。 msg）{
 TotalOBValueLand + = parseInt（msg.data [0] .OBValueLand）; 
 //我在这里返回的数据没有错误
}）; 
} 
 console.log（TotalOBValueLand）; //我有零; 
  

解决方案使用 Promise.all 和数组＃map 得到一个结果数组，然后使用Array＃reduce将它们加起来

  var TotalOBValueLand = 0; 
 Promise.all（$ scope.selectedProp.map（function（prop）{
 return AccountService.getTopAccountDetails（prop）.then（function（msg）{
 return parseInt（msg.data [ 0）.OBValueLand）; 
}）; 
}））then（function（results）{
 TotalOBValueLand = results.reduce（function（a，b）{
 return a + b; 
}）; 
 console.log（TotalOBValueLand）; 
}）; 
  

回复评论

  var TotalOBValueLand = 0; 
 var TotalOBValueBuilding = 0; 
 Promise.all（$ scope.selectedProp.map（function（prop）{
 return AccountService.getTopAccountDetails（prop）.then（function（msg）{
 return parseInt（msg.data [ 0））; 
}）; 
}））。then（function（results）{
 TotalOBValueLand = results.reduce（function（a，b）{
 return a。 OBValueLand + b.OBValueLand; 
））; 
 TotalOBValueBuilding = results.reduce（function（a，b）{
 return a.OBValueBuilding + b.OBValueBuilding; 
}）; 
 console.log（TotalOBValueLand，TotalOBValueBuilding）; 
}）; 
  

更通用一些

  Promise.all（$ scope.selectedProp.map（function（prop）{
 return AccountService.getTopAccountDetails（prop） .then（function（msg）{
 return parseInt（msg.data [0]）; 
}）; 
}））。then（function（results）{
 var totalals = results.reduce（function（result，a）{
 Object.keys（a）.forEach（function（key）{
 result [key] =（result [key] || 0）+一个[键]; 
））; 
返回结果; 
}，{}）; 
 console.log（totals.OBValueLand，totals.OBValueBuilding）; 
 }）; 
  

I have a angular service inside a for loop that returns an array of object. I want to get the summation of the value returned by that service but I got nothing in the end. My service works fine but my problem is I can't get the summation. Below is my code

controller

var TotalOBValueLand = 0;
for(var i = 0; i < $scope.selectedProp.length; i++){
     AccountService.getTopAccountDetails($scope.selectedProp[i]["propId"]).then(function(msg){
           TotalOBValueLand += parseInt(msg.data[0].OBValueLand);
           //my return data here has no error.
     });
}
console.log(TotalOBValueLand); //I got zero;

解决方案

Use Promise.all and array#map to get an array of results, then use Array#reduce to sum them up

var TotalOBValueLand = 0;
Promise.all($scope.selectedProp.map(function(prop) {
     return AccountService.getTopAccountDetails(prop).then(function(msg){
           return parseInt(msg.data[0].OBValueLand);
     });
})).then(function(results) {
    TotalOBValueLand = results.reduce(function(a, b) {
       return a + b; 
    });
    console.log(TotalOBValueLand);
});

In response to the comments

var TotalOBValueLand = 0;
var TotalOBValueBuilding = 0;
Promise.all($scope.selectedProp.map(function(prop) {
     return AccountService.getTopAccountDetails(prop).then(function(msg){
           return parseInt(msg.data[0]);
     });
})).then(function(results) {
    TotalOBValueLand = results.reduce(function(a, b) {
       return a.OBValueLand + b.OBValueLand; 
    });
    TotalOBValueBuilding  = results.reduce(function(a, b) {
       return a.OBValueBuilding  + b.OBValueBuilding ; 
    });
    console.log(TotalOBValueLand, TotalOBValueBuilding);
});

and a little more generic

Promise.all($scope.selectedProp.map(function(prop) {
     return AccountService.getTopAccountDetails(prop).then(function(msg){
           return parseInt(msg.data[0]);
     });
})).then(function(results) {
    var totals = results.reduce(function(result, a) {
        Object.keys(a).forEach(function(key) {
            result[key] = (result[key] || 0) + a[key];
        });
        return result;
    }, {});
    console.log(totals.OBValueLand, totals.OBValueBuilding);
});

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