Angular 离子4:无法读取属性';获取';未定义的
我试图通过Angular 离子4:无法读取属性';获取';未定义的,angular,typescript,ionic-framework,ionic4,Angular,Typescript,Ionic Framework,Ionic4,我试图通过get()函数从数据库中获取一些信息,但是当我尝试运行时,它会得到标题错误,声明 at HomeTabPage.push ../src/app/home-tab/home-tab.page.ts.HomeTabPage.ngOnInit (home-tab.page.ts: 18) 不,因为我已经尝试使用Elvis参数,但它不起作用。我已经将我的主函数从ngOnInit中传递出去,并声明了另一个要引用的函数,但它不起作用 主页选项卡.page.html 错误 HomeTabPag
get()
函数从数据库中获取一些信息,但是当我尝试运行时,它会得到标题错误,声明
at HomeTabPage.push ../src/app/home-tab/home-tab.page.ts.HomeTabPage.ngOnInit (home-tab.page.ts: 18)
不,因为我已经尝试使用Elvis参数,但它不起作用。我已经将我的主函数从ngOnInit中传递出去,并声明了另一个要引用的函数,但它不起作用
主页选项卡.page.html
错误
HomeTabPage_Host.ngfactory.js? [sm]:1 ERROR TypeError: Cannot read property 'get' of undefined
at HomeTabPage.push../src/app/home-tab/home-tab.page.ts.HomeTabPage.ngOnInit (home-tab.page.ts:18)
at checkAndUpdateDirectiveInline (core.js:22099)
at checkAndUpdateNodeInline (core.js:23363)
at checkAndUpdateNode (core.js:23325)
at debugCheckAndUpdateNode (core.js:23959)
at debugCheckDirectivesFn (core.js:23919)
at Object.eval [as updateDirectives] (HomeTabPage_Host.ngfactory.js? [sm]:1)
at Object.debugUpdateDirectives [as updateDirectives] (core.js:23911)
at checkAndUpdateView (core.js:23307)
at callViewAction (core.js:23548)
好的,有一个场景没有被代码处理。如果
firebase.auth().onAuthStateChanged
中未定义user
,该怎么办?您的this.adAllListRef
将不会被初始化,因此在这种情况下您也会得到相同的错误
我可能无法给出有效的代码,但我可以建议您处理此问题的方法:
由于此页面仅在用户
有效时才起作用,因此请尝试使用如下内容:
import { Injectable } from '@angular/core';
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot, Router, Route } from '@angular/router';
import { Observable } from 'rxjs';
@Injectable()
export class AuthGuard implements CanActivate {
constructor(private _router: Router,private _advSvc: AdvertisingService) {
}
canActivate(next: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<boolean>
{
return new Promise((resolve) => {
firebase.auth().onAuthStateChanged(user => {
if (user) {
resolve(true);
}else{
this._router.navigate(['/login']);
resolve(false);
}
});
}
}
并将路由器定义为:
const route = [
{ .... },
{path: '/home',component: HomeTabPage, canActivate: [AuthGuard] },
{path: '/login',component: LoginPage }
]
发布服务代码问题不在于模板,而在于typescript代码。看这一行
this.adService.getAdAllList().get()。然后(…
它看起来像'getAdAllList()返回null,因此在未定义的值上调用get会引发错误。我发布了服务代码。你说的很有道理。使用此代码,我放置了service.ts,我试图请求的路径是错误的?我应该传递任何参数吗?你的问题是,你试图在它准备好之前访问它。我没有与Firebase合作过f我的建议是,我的意思是,Firebase很难找到一个好的Firebase教程,然后回到基础,否则即使它提供了ded.工作得很好。我举了一个使用firebase的例子,但没有意识到我需要在每次打开app.ty时查看用户是否登录
HomeTabPage_Host.ngfactory.js? [sm]:1 ERROR TypeError: Cannot read property 'get' of undefined
at HomeTabPage.push../src/app/home-tab/home-tab.page.ts.HomeTabPage.ngOnInit (home-tab.page.ts:18)
at checkAndUpdateDirectiveInline (core.js:22099)
at checkAndUpdateNodeInline (core.js:23363)
at checkAndUpdateNode (core.js:23325)
at debugCheckAndUpdateNode (core.js:23959)
at debugCheckDirectivesFn (core.js:23919)
at Object.eval [as updateDirectives] (HomeTabPage_Host.ngfactory.js? [sm]:1)
at Object.debugUpdateDirectives [as updateDirectives] (core.js:23911)
at checkAndUpdateView (core.js:23307)
at callViewAction (core.js:23548)
import { Injectable } from '@angular/core';
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot, Router, Route } from '@angular/router';
import { Observable } from 'rxjs';
@Injectable()
export class AuthGuard implements CanActivate {
constructor(private _router: Router,private _advSvc: AdvertisingService) {
}
canActivate(next: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<boolean>
{
return new Promise((resolve) => {
firebase.auth().onAuthStateChanged(user => {
if (user) {
resolve(true);
}else{
this._router.navigate(['/login']);
resolve(false);
}
});
}
}
export class AdvertisingService {
constructor() {
}
getAdAllList(): firebase.firestore.CollectionReference {
return firebase.firestore().collection(`/adverts/adAll/adList`);
}
}
const route = [
{ .... },
{path: '/home',component: HomeTabPage, canActivate: [AuthGuard] },
{path: '/login',component: LoginPage }
]