如何修复错误 "this.accountService is undefined"

Question

我是 Angular 和 JHipster 的新手。请帮助解决问题。我没有更改那里的代码。有jhipster的默认登录密码。

堆栈跟踪：

TypeError: this.accountService 未定义堆栈跟踪： LoginService.prototype.logout@webpack-internal:///./src/main/webapp/app/core/login/login.service.ts:33:9 NavbarComponent.prototype.logout@webpack-internal:///./src/main/webapp/app/layouts/navbar/navbar.component.ts:49:9 View_NavbarComponent_30/<@ng:///NgrkAppModule/NavbarComponent.ngfactory.js:1470:23

core/login/login.service.ts:

import { AccountService } from 'app/core/auth/account.service';

--------------------------------------------------

constructor(private accountService: AccountService)

--------------------------------------------------

    login(credentials, callback?) {
        const cb = callback || function() {};

        return new Promise((resolve, reject) => {
            this.authServerProvider.login(credentials).subscribe(
                data => {
                    this.accountService.identity(true).then(account => {
                        resolve(data);
                    });
                    return cb();
                },
                err => {
                    this.logout();
                    reject(err);
                    return cb(err);
                }
            );
        });
    }


    logout() {
        this.authServerProvider.logout().subscribe();
        this.accountService.authenticate(null);
    }

core/auth/account.service.ts:

export class AccountService {
--------------------------------

    authenticate() {
      some code;
    }

    identity() {
      some code;
    }

--------------------------------
}

Answer 1

如果 this 处理不当，读取 this 的内容并发现它是 undefined 是一个常见问题。

修复

快速修复是将 an arrow 用于 logout：

logout = () => {

并可能在其他地方使用它（例如 login）以及为了将来的安全。

Answer 2

您可以在 Promise 外部保留对此的引用并使用它来代替它。

login(credentials, callback?) {
    let that = this;
    const cb = callback || function() {};

    return new Promise((resolve, reject) => {
        that.authServerProvider.login(credentials).subscribe(
            data => {
                that.accountService.identity(true).then(account => {
                    resolve(data);
                });
                return cb();
            },
            err => {
                that.logout();
                reject(err);
                return cb(err);
            }
        );
    });
}

同时将 @Injectable() 添加到您的 AccountService class

 @Injectable()
export class AccountService

如何修复错误 "this.accountService is undefined"

How to fix an error "this.accountService is undefined"

login

typescript

jhipster

angular

修复