typescript 元素访问表达式应该带一个参数
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An element access expression should take an argument
提问by Hemant
I am new to Angular I have tried to create some sample application but getting error. Please help. I am trying to make my own from googles project (https://stackblitz.com/angular/ooqemvjyqkb?file=src%2Fapp%2Fheroes%2Fheroes.component.ts) When I remove array from "users = User[];" it works fine but it does not give a build([ts] Type 'User[]' is not assignable to type 'typeof User'.). With "users = User[];" it does not even compile(suggestion [ts] An element access expression should take an argument.(any)) .
我是 Angular 的新手，我尝试创建一些示例应用程序，但出现错误。请帮忙。我正在尝试从 googles 项目（https://stackblitz.com/angular/ooqemvjyqkb?file=src%2Fapp%2Fheroes%2Fheroes.component.ts）中创建自己的项目，当我从“users = User[];”中删除数组时 它工作正常，但它没有提供构建（[ts] 类型 'User[]' 不可分配给类型 'typeof User'。）。随着“用户=用户[];” 它甚至不 compile(suggestion [ts] An element access expression should take an argument.(any)) 。
import { Component, OnInit } from '@angular/core';
import { User } from '../user';
import { UserService } from '../user.service';
@Component({
selector: 'app-users',
templateUrl: './users.component.html',
styleUrls: ['./users.component.css']
})
export class UsersComponent implements OnInit {
selectedUser: User;
users = User[]; // review use of array type. users = User[];
constructor(
private userService: UserService
) { }
ngOnInit() {
this.getUsers();
}
onSelect(user: User): void {
this.selectedUser = user;
}
getUsers(): void {
this.userService.getUsers()
.subscribe(users => this.users = users);
}
save(): void {
this.userService.updateUser(this.users);
}
add(name: string): void {
console.log(name);
name = name.trim();
if (!name) { return; }
this.userService.addUser({ name } as User)
.subscribe(user => {
this.users.push(user);
});
}
}
////////////////////user.ts///////////////
///////////////////user.ts///////////////
export class User {
id: number;
name: string;
}
///////////////user.service.ts////////////////
///////////////user.service.ts////////////////
import { Injectable } from '@angular/core';
import { Observable, of } from 'rxjs';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { User } from './user';
// import { USERS } from '../assets/data/userData';
const httpOptions = {
headers: new HttpHeaders({ 'Content-Type': 'application/json' })
};
@Injectable({ providedIn: 'root' })
export class UserService {
private usersUrl = 'api/users';
constructor(
private http: HttpClient) { }
getUsers(): Observable<User[]> {
// return of(USERS);
return this.http.get<User[]>(this.usersUrl);
}
/** GET user by id. Will 404 if id not found */
getUser(id: number): Observable<User> {
const url = `${this.usersUrl}/${id}`;
return this.http.get<User>(url);
}
/** PUT: update the user on the server */
updateUser (user: User): Observable<any> {
return this.http.put(this.usersUrl, user, httpOptions);
}
/** POST: add a new user to the server */
addUser (user: User): Observable<User> {
return this.http.post<User>(this.usersUrl, user, httpOptions);
}
/* GET users whose name contains search term */
searchUsers(term: string): Observable<User[]> {
if (!term.trim()) {
// if not search term, return empty hero array.
return of([]);
}
return this.http.get<User[]>(`${this.usersUrl}/?name=${term}`);
}
}
回答by D1ZZYD 23
Replace
代替
users = User[];
with
和
user: User[]
That should do the trick.
这应该够了吧。
回答by Pipo
The correct syntax for me was not
对我来说正确的语法不是
user: User[] = User[] // WRONG SYNTAX
but
但
users: User[] = []
or
或者
users: User[] = new Array<User>()
回答by amracel
Try:
尝试：
users = [Users];
I find that syntax tends to work better.
我发现语法往往效果更好。
回答by 4dc0
I just ran into this trying to compile a standalone typescript file with tsc. In my case I had to change this:
我刚刚在尝试使用 tsc 编译一个独立的打字稿文件时遇到了这个问题。就我而言，我不得不改变这一点：
users: User[];
to this:
对此：
let users: User[];
回答by Zubair A.
do not adding users = User[], as you are getting users from service. instead just declare the type like users: User[];
不要添加用户 = 用户 []，因为您是从服务中获取用户的。相反，只需声明类型，如 users: User[];
Above will work
以上将工作
回答by Moritz Lüdtke
As some people wrote before, you try to add User[]which is an array to a method that only needs one single user. You access one element of an arry, by writing the following code:
正如一些人之前写的那样，您尝试将User[]which 是一个数组添加到只需要一个用户的方法中。您可以通过编写以下代码访问 arry 的一个元素：
save(): void {
this.userService.updateUser(this.users[THE_INDEX_FROM_THE_CURRENT_USER]);
}
That should only give one Userto the updateUser()
这应该只给一个User到updateUser()
So in general:
所以一般来说：
oneArray: Foo[]; <- creates an array named 'oneArray' with Foo objects inside
oneFoo = oneArray[0]; <- Gives you the first element of the array
