Angular EventEmitter类型错误：预期0个类型参数却传入1个

我刚解决了和你一模一样的问题！咱们来一步步搞定它：

问题回顾 #

你遇到了两个关联的TypeScript错误：

• 当你声明带有类型参数的EventEmitter时：

  @Output() newUserInfoCompleteEvent = new EventEmitter<boolean>();
  

  报错：Expected 0 type arguments, but got 1
• 去掉<boolean>后，调用emit方法时：

  this.newUserInfoCompleteEvent.emit(this.newUserInfoComplete);
  

  又报错：Argument of type 'boolean' is not assignable to parameter of type 'string'

错误根源 #

看你的组件导入语句，你错误地从protractor导入了EventEmitter：

import { EventEmitter } from 'protractor';

Protractor的EventEmitter是为端到端测试设计的，它不支持泛型类型参数，而且默认只接受string类型的参数——这就是两个错误的核心原因！

修复步骤 #

1. 修正EventEmitter的导入来源：把EventEmitter从@angular/core导入，而不是protractor。修改你的导入语句：

   import { Component, OnInit, Output, EventEmitter } from '@angular/core';
   

   同时删掉单独的import { EventEmitter } from 'protractor';这一行。

2. 保留正确的泛型类型参数：你的EventEmitter声明是对的，继续保留<boolean>：

   @Output() newUserInfoCompleteEvent = new EventEmitter<boolean>();
   

3. 验证emit调用：现在调用this.newUserInfoCompleteEvent.emit(this.newUserInfoComplete)时，TypeScript会正确识别boolean类型，不会再报错。

修正后的完整组件代码 #

import { Component, OnInit, Output, EventEmitter } from '@angular/core';
import { slideToRight } from '../../../../router.animations';
import { Router, ActivatedRoute, UrlSegment } from '@angular/router';

@Component({
  selector: 'app-new-user-input',
  templateUrl: './new-user-input.component.html',
  styleUrls: ['./new-user-input.component.css'],
  animations: [slideToRight()]
})
export class NewUserInputComponent implements OnInit {
  newUserInfoComplete: boolean = false;

  @Output() newUserInfoCompleteEvent = new EventEmitter<boolean>();

  constructor(private router: Router, r: ActivatedRoute) {
    r.url.subscribe((s: UrlSegment[]) => {
      console.log("url", s);
    });
  }

  ngOnInit() { }

  sendNewUserInfoComplete(){
    this.newUserInfoCompleteEvent.emit(this.newUserInfoComplete);
  }

  displaySibling() {
    console.log(this.router);
    this.router.navigate(['../', { outlets: { newuserorginfo: ['newuserorginfo'] } }])
  }

  closeBlade() {
    this.router.navigate([{ outlets: { newuserinput: null } }]);
  }
}

内容的提问来源于stack exchange，提问作者imnickvaughn