Question

我在角色中遇到了<select>元素的多个问题，并试图了解正在发生的事情。我的第一步是理解为什么我调入的多个console.log()消息重复出现在控制台中，就像在，而不是像我期望的那样出现的消息，它们出现无限次，如如果是无限循环的一部分。这是一个从ng-options调用的函数应该如何表现的？如果是这样，我不明白为什么，如果没有，那么我想修复我的循环。

我的HTML：<select ng-options="theorderdate as theorderdate for theorderdate in getOtherOrderDates(Bread.text)" ng-model="randomDateRomantic.randomDateRomantic" ng-change="soRomantic(Bread.text)"></select>

console.log()消息显示getOtherOrderDates()消息，如下所示（包括我的评论）：

$scope.getOtherOrderDates = function(loaf) {
  var istheLoafdaily = false;
  var theorderdates = [];
  for (var i = 0; i < $scope.theBreadsList.length; i++) {
    for (var z = 0; z < $scope.theBreadsList[i].breads.length; z++) {
      if ($scope.theBreadsList[i].breads[z].text == loaf && i > 0) //not a daily loaf, goes beyond "Daily Breads" 
      {
        console.log(theorderdates);
        theorderdates = theorderdates.concat($scope.theBreadsList[i].breads[z].orderDates); //concat the matched bread's order dates
        console.log(theorderdates, $scope.theBreadsList[i].breads[z].orderDates);
        theorderdates = _.sortBy(theorderdates, function(m) {
          return m.getTime()
        });
        for (var y = 0; y < theorderdates.length; y++) {
          theorderdates[y] = theorderdates[y].toLocaleDateString();
        }
        theorderdates = _.uniq(theorderdates);
        if (theorderdates.length > 0) {
          console.log("Something is wrong here"); //problem
          $scope.randomDateRomantic.randomDateRomantic = theorderdates[0];
        }
        console.log(theorderdates);
        return theorderdates;
      } else if ($scope.theBreadsList[i].breads[z].text == loaf && i == 0) { //a daily loaf, i == 0
        console.log("The bread matched is daily", loaf); //***
        istheLoafdaily = true;
        console.log(theorderdates); //***
        theorderdates = theorderdates.concat($scope.theBreadsList[i].breads[z].orderDates); // concat the matched bread's order dates
        console.log(theorderdates, $scope.theBreadsList[i].breads[z].orderDates); //***
        break; // escape the for loop, should it be two breaks?????? yes...
      } else if (istheLoafdaily && i > 0 && $scope.theBreadsList[i].breads[z].orderDates.length > 0) { //not sure what scenario this matches, hence wtf
        theorderdates = theorderdates.concat($scope.theBreadsList[i].breads[z].orderDates);
        console.log("wtf");
      }

    }
  }
  //end of outermost for loop
  //not sure what this is doing because this functionality is repeated up there^ (for non-daily breads)
  theorderdates = _.sortBy(theorderdates, function(m) {
    return m.getTime()
  });
  for (var y = 0; y < theorderdates.length; y++) {
    theorderdates[y] = theorderdates[y].toLocaleDateString();
  }
  theorderdates = _.uniq(theorderdates);

  if (theorderdates.length > 0) {
    $scope.randomDateRomantic.randomDateRomantic = theorderdates[0];
    console.log("Something is wrong here (daily)"); //problem
  }
  return theorderdates;
  //not sure what this is doing because this functionality is repeated up there^ (for non-daily breads)
  //if change to Locale date string then not unique, but if don't change then not a date to sort!!!!!!! >:(
},

我几乎无法获得所有控制台消息，而没有执行任何操作，例如触发ng-change函数。我只是将每日面包添加到我的购物车中，然后控制台充满了以下消息，我已经在我的代码中加了星号。

我的theBreadsList不是很长，所以有一些事情会像这样反复发生。即使我在代码中看到两次for循环中断，也无法解释它一直记录到控制台的事实，因为最终循环不会得到满足，而且这不会只要已经提到过。

请指教，谢谢。如果您需要更多信息，我很乐意提供。

Answer 1

每个digest cycle都会调用getOtherOrderDates，以便有角度的知道是否更新option中的select。这很可能是您多次看到此方法被调用的原因。

如果您担心此循环对性能的影响，您可以在controller $scope内预先构建选项，如下所示：

$scope.options = $scope.getOtherOrderDates($scope.Bread.text);

每当$scope.Bread.text更改，然后在模板中使用$scope.options。

Answer 2

为了避免在每个摘要循环中触发循环，您可以使用一次绑定::value。

<select ng-options="theorderdate as theorderdate for theorderdate in ::getOtherOrderDates(Bread.text)" 
        ng-model="randomDateRomantic.randomDateRomantic" 
        ng-change="soRomantic(Bread.text)"></select>

由于ng-options中的表达式只会被评估一次，并且在第一次评估后将会删除观察器，这将阻止您的函数在下一个摘要循环迭代中被触发。

DOCS

重复调用Ng-Options表达式

2 个答案: