Question

我试图使用lodash和angularfire2遍历用户数据数组但是我得到错误TypeError：无法读取属性＆＃39; db＆＃39;未定义的

典型的推送阵列 [ 0：user1， 1：user2， 2：user3， ]

            import { AngularFireDatabase} from 'angularfire2/database';
            import { AngularFireAuth } from 'angularfire2/auth';
            import * as firebase from 'firebase/app';;
            import * as _ from 'lodash';

            constructor( 
                private db             : AngularFireDatabase, 
                private afAuth         : AngularFireAuth) {}




            addGroupChats(allGroupMember) {
            console.log("allGroupMember", allGroupMember);

              //this line work well without error
              console.log("value[0]", allGroupMember.users[0]);
              //let endpoint = this.db.object(`/users/${allGroupMember.users[0]}/groups/${allGroupMember.groupUid}`);
              //endpoint.set(true); 

                this line throws ERROR TypeError: Cannot read property 'db' of undefined
              _.forEach(allGroupMember.users, function(value) {
                  let endpoint = this.db.object(`/users/${value}/groups/${allGroupMember.groupUid}`);
                  endpoint.set(true);      
              });
            }

Answer 1

您需要使用arrow functions进行回调。 this引用函数对象而不是您的案例中的类。这里：

_.forEach(allGroupMember.users,(value) => {
                  let endpoint = this.db.object(`/users/${value}/groups/${allGroupMember.groupUid}`);
                  endpoint.set(true);      
              })

ERROR TypeError：无法读取属性＆＃39; db＆＃39;未定义的

1 个答案: