Angular ngChange 处理程序获取旧值

本文介绍了Angular ngChange 处理程序获取旧值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我正在创建 angular 指令，它用引导程序表单组包装 html 输入.我使用 ng-change 事件来监听更改，但我在 ng-change 处理程序中获得了旧值.为了说明这一点，我创建了相同的指令，一个使用 ng-keyup，另一个使用 ng-change 事件来监听更改.

I am creating angular directive, which wraps html input with bootstrap form group. I use ng-change event to listen to changes, but I get old value inside ng-change handler.To show this, I created to identical directives, one uses ng-keyup and another uses ng-change event to listen to changes.

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

app.controller('home', function() {
  this.textKeyUp = 'KeyUp';
  this.textNgChange = 'NgChange';

  this.textKeyUpChanged = function() {
    console.log('Changed on KeyUp:', this.textKeyUp);
  };

  this.textNgChangeChanged = function() {
    console.log('Changed on NgChange:', this.textNgChange);
  };
});

app.directive('apTextKeyUp', function() {
  return {
    controller: function() {},
    controllerAs: 'ctrl',
    bindToController: {
      model: '=',
      change: '&'
    },
    scope: {},
    template: '<input ng-model="ctrl.model" ng-keyup="ctrl.change()" />'
  };
});


app.directive('apTextNgChange', function() {
  return {
    controller: function() {},
    controllerAs: 'ctrl',
    bindToController: {
      model: '=',
      change: '&'
    },
    scope: {},
    template: '<input ng-model="ctrl.model" ng-change="ctrl.change()" />'
  };
});

<!DOCTYPE html>
<html ng-app="app">
  <head>
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.5/angular.min.js"></script>
  </head>
  <body ng-controller="home as ctrl">
    <h3>KeyUp</h3>
    <ap-text-key-up model="ctrl.textKeyUp" change="ctrl.textKeyUpChanged()"></ap-text-key-up>

    <h3>NgChange</h3>
    <ap-text-ng-change model="ctrl.textNgChange" change="ctrl.textNgChangeChanged()"></ap-text-ng-change>
  </body>
</html>

两个指令都更新模型值，但内部 textNgChangeChanged 处理程序值尚未更新.

Both directives update model value, but inside textNgChangeChanged handler value is not updated yet.

这是故意的吗?我该如何解决这个问题?

Is this by design? How can I fix this problem?

推荐答案

看起来当使用 Primative 类型作为 ng-model 值时，当值改变时会调用 ng-change.由于这是原始类型，因此该值尚未传播到 homeCtroller.如果您将指令传递给一个引用对象，那么事情会按预期工作.

It looks like when using Primative type as the ng-model value, ng-change will be invoke when the value is changed. Since this is a primative type, the value hasn't been propagated to the homeCtroller. If you pass the directive a reference object, things work as expected.

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

app.controller('home', function() {
  this.text = {val: 'ABC'};
  this.textChanged = function() {
    console.log('Changed:', this.text.val);
  };
});

app.directive('apText', function() {
  return {
    controller: function() {
      var vm = this;
      vm.onChange = function(){
        console.log(vm.model);
        vm.change();
      };
    },
    controllerAs: 'ctrl',
    bindToController: {
      model: '=',
      change: '&'
    },
    scope: true,
    template: '<input ng-model="ctrl.model.val" ng-change="ctrl.onChange()" />'
  };
});

<!DOCTYPE html>
<html ng-app="app">

  <head>
    <link rel="stylesheet" href="style.css" />
    <script src="https://code.angularjs.org/1.5.0-rc.0/angular.js"></script>
    <script src="script.js"></script>
  </head>

  <body ng-controller="home as ctrl">
    <ap-text model="ctrl.text" change="ctrl.textChanged()"></ap-text>
  </body>

</html>

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

app.controller('home', function() {
  this.text = 'ABC';
  this.textChanged = function() {
console.log('Changed:', this.text);
  };
});

app.directive('apText', function() {
  return {
controller: function() {
  var vm = this;
  vm.onChange = function(){
    console.log(vm.model);
    vm.change();
  };
},
controllerAs: 'ctrl',
bindToController: {
  model: '=',
  change: '&'
},
scope: true,
template: '<input ng-model="ctrl.model" ng-change="ctrl.onChange()" />'
  };
});

<!DOCTYPE html>
<html ng-app="app">

  <head>
    <link rel="stylesheet" href="style.css" />
    <script src="https://code.angularjs.org/1.5.0-rc.0/angular.js"></script>
    <script src="script.js"></script>
  </head>

  <body ng-controller="home as ctrl">
    <ap-text model="ctrl.text" change="ctrl.textChanged()"></ap-text>
  </body>

</html>

这篇关于Angular ngChange 处理程序获取旧值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！