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问angular.copy的使用
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Stack Overflow用户

提问于 2019-06-26 02:25:38

回答 2查看 345关注 0票数 1

我使用的是angular.copy，但它在循环对象和赋值变量方面也很好。

与循环需要赋值的变量相比，angular.copy还有什么用途？

angularjs

回答 2

Stack Overflow用户

回答已采纳

发布于 2019-06-26 04:46:43

当将对象或数组的值赋值给另一个变量时，请使用angular.copy，并且不应更改该对象值。

如果不使用深度复制或使用angular.copy，则更改属性值或添加任何新的属性都会更新引用同一对象的所有对象。

角: js文件

var app = angular.module('copyExample', []);
app.controller('ExampleController', ['$scope',
  function($scope) {
    $scope.printToConsole = function() {
      $scope.main = {
        first: 'first',
        second: 'second'
      };

      $scope.child = angular.copy($scope.main);
      console.log('Main object :');
      console.log($scope.main);
      console.log('Child object with angular.copy :');
      console.log($scope.child);

      $scope.child.first = 'last';
      console.log('New Child object :')
      console.log($scope.child);
      console.log('Main object after child change and using angular.copy :');
      console.log($scope.main);
      console.log('Assing main object without copy and updating child');

      $scope.child = $scope.main;
      $scope.child.first = 'last';
      console.log('Main object after update:');
      console.log($scope.main);
      console.log('Child object after update:');
      console.log($scope.child);
    }
  }
]);

// Basic object assigning example

var main = {
  first: 'first',
  second: 'second'
};
var one = main; // same as main
var two = main; // same as main

console.log('main :' + JSON.stringify(main)); // All object are same
console.log('one :' + JSON.stringify(one)); // All object are same
console.log('two :' + JSON.stringify(two)); // All object are same

two = {
  three: 'three'
}; // two changed but one and main remains same
console.log('main :' + JSON.stringify(main)); // one and main are same
console.log('one :' + JSON.stringify(one)); // one and main are same
console.log('two :' + JSON.stringify(two)); // two is changed

two = main; // same as main

two.first = 'last'; // change value of object's property so changed value of all object property 

console.log('main :' + JSON.stringify(main)); // All object are same with new value
console.log('one :' + JSON.stringify(one)); // All object are same with new value
console.log('two :' + JSON.stringify(two)); // All object are same with new value

对应代码：

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>

<div ng-app="copyExample" ng-controller="ExampleController">
  <button ng-click='printToConsole()'>Explain</button>
</div>

票数 0

Stack Overflow用户

发布于 2019-06-26 04:19:19

angular.copy()创建一个新的对象作为一个深拷贝，这意味着这两个对象将相互独立。

在执行常规循环和赋值时，假设您使用的是=运算符，这意味着更改原始对象的属性将更改复制对象的相应属性，反之亦然。

例如，考虑一个对象：

let obj1 = {something};

let obj2; //you want to copy obj1 into obj2

//case 1: using angular.copy
obj2 = angular.copy(obj1);  

//case 2: using =
obj2 = obj1;