ng-model:空字符串应该为空 [英] ng-model: empty strings should be null

问题描述

如果我使用 ng-model 作为输入字段并将其清空，angular 会将其设置为 '' 而不是 null，即使它是之前是 null.

If I use ng-model for an input field and empty it, angular sets it to '' instead of null even if it was null before.

这对我来说是个问题，因为如果输入字段为空，我需要将 null 发送到服务器，而不是 ''.

This is a problem in my case because I need to send null to the server if the input field is empty, and not ''.

有没有办法告诉角度设置空"输入模型为null?

Is there a way to tell angular setting "empty" input models to null?

推荐答案

您可能希望 $watch 为空值并将其设置为 null:

You may want to $watch for the empty value and set it to null:

<input type="text" ng-model="test.value" />

$scope.$watch('test.value', function (newValue, oldValue) {
  if(newValue === "")
    $scope.test.value = null;
});

另一种方法是使用自定义指令并在其中应用 $parsers:

Another way would be to use a custom directive and apply a $parsers in it:

<input type="text" ng-model="test.value" empty-to-null />

myApp.directive('emptyToNull', function () {
    return {
        restrict: 'A',
        require: 'ngModel',
        link: function (scope, elem, attrs, ctrl) {
            ctrl.$parsers.push(function(viewValue) {
                if(viewValue === "") {
                    return null;
                }
                return viewValue;
            });
        }
    };
});

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