[AngularJS] Isolate State Mutations in Angular Components
Managing state is one of the hardest things to do in any application. Angular 2 tackles this problem by making it easy to implement a reactive, uni-directional data flow that favor immutable operations. We are moving in the right direction in Angular 1 by moving our state and logic to models but invariably this raises a question. If we are moving to an immutable world, how do you manage mutable operations like forms in Angular? In this lesson, we are going to learn a surprisingly simple technique to isolate state mutations within a component using component lifecycle hooks.
For example you have a bookmark component, and inside the component, you want to update the bookmark. The solution is you create a component just for update bookmark.
<div class="bookmarks"> <div ng-repeat="bookmark in bookmarksListCtrl.bookmarks | filter:{category:bookmarksListCtrl.getCurrentCategory().name}"> <button type="button" class="close" ng-click="bookmarksListCtrl.deleteBookmark(bookmark)">×</button> <button type="button" class="btn btn-link" ng-click="bookmarksListCtrl.editBookmark(bookmark)"> <span class="glyphicon glyphicon-pencil"></span> </button> <a href="{{bookmark.url}}" target="_blank">{{bookmark.title}}</a> </div> <div ng-if="bookmarksListCtrl.getCurrentCategory()"> <button type="button" class="btn btn-link" ng-if="!bookmarksListCtrl.currentBookmark" ng-click="bookmarksListCtrl.createBookmark()"> <span class="glyphicon glyphicon-plus"></span> Create Bookmark </button> </div> <save-bookmark ng-if="bookmarksListCtrl.currentBookmark" bookmark="bookmarksListCtrl.currentBookmark" save="bookmarksListCtrl.onSave(bookmark)" cancel="bookmarksListCtrl.reset()"> </save-bookmark> </div>
And inside the save-bookmark component, you can copy the original data, and modify on the copy data:
class SaveController { $onChanges() { this.editedBookmark = Object.assign({}, this.bookmark); } } export default SaveController;
This can isolate the component state muataion.