Angular 2：找不到 ngOnInit/ngOnDestroy答案

【问题标题】：Angular 2: Cannot find ngOnInit/ngOnDestroyAngular 2：找不到 ngOnInit/ngOnDestroy
【发布时间】：2018-12-12 00:02:32
【问题描述】：

注意：我找到了文章cannot find OnInit in typescript during implementation，但下面的代码已经在导入OnInit/OnDestroy。

我发现的所有示例（例如，Using Route Parameters）都表明将implements OnInit/OnDestroy 子句添加到类定义中，并在订阅以获取参数时包括ngOnInit/ngOnDestroy 方法路线——代码正在做的事情。

但是VS2017子句报错“incorrectly implements OnInit/OnDestroy”，函数报错“Cannot find ngOnInit/ngOnDestroy”。

如果我删除implements 子句并注释ngOnInit/ngOnDestroy 函数（仅在ngOnInit 的主体中留下代码），则代码有效；成功从路由参数中获取参数。

import { Component, Inject, OnInit, OnDestroy } from '@angular/core';
import { Http } from '@angular/http';
import { ActivatedRoute } from '@angular/router';

@Component({
    selector: 'submission',
    templateUrl: './submission.component.html'
})
export class SubmissionComponent implements OnInit, OnDestroy {
    private baseUrl: string;
    private http: Http;
    private route: ActivatedRoute;
    private sub: any;

    public caseId: string;
    public submission: Submission;

    constructor(http: Http, route: ActivatedRoute, @Inject('BASE_URL') baseUrl: string) {
        this.http = http;
        this.route = route;
        this.baseUrl = baseUrl;

        ngOnInit() {
            this.sub = this.route.params.subscribe(params => {
                this.caseId = params['caseId'];

                // In a real app: dispatch action to load the details here.
            });
        }

        ngOnDestroy() {
            this.sub.unsubscribe();
        }

        this.get(this.caseId);
    }

    public get(caseId: string) {
        var url = this.baseUrl + 'api/Submission/GetSubmission?caseId=' + caseId;
        this.http.get(url).subscribe(result => {
            this.submission = result.json() as Submission;
        }, error => console.error(error));
    }

    public put() {
        var url = this.baseUrl + 'api/Submission/PutSubmission';
        this.http.put(url, this.submission).subscribe(result => {
            this.submission = result.json() as Submission;
        }, error => console.error(error));
    }
}

【问题讨论】：

标签： angular implements ngoninit ngondestroy

【解决方案1】：

我可以从你的代码中看到 ngOnInit 和 ngOnDestroy 在构造函数中，所以如果你把它放在外面应该没问题。

代码示例：

constructor(http: Http, route: ActivatedRoute, @Inject('BASE_URL') baseUrl: string) {
    this.http = http;
    this.route = route;
    this.baseUrl = baseUrl;
}

ngOnInit() {
    this.sub = this.route.params.subscribe(params => {
      this.caseId = params['caseId'];

      this.get(this.caseId);

      // In a real app: dispatch action to load the details here.
    });
}

ngOnDestroy() {
  this.sub.unsubscribe();
}

通常，在添加 ngOnInit 和 ngOnDestroy 时，您应该始终检查以下步骤：

检查您是否已从“angular/core”导入 OnInit 和 OnDestroy
然后将它们添加到类中

添加这些功能

import { OnInit, OnDestroy } from '@angular/core';
export class ComponentComponent implements OnInit, OnDestroy {
  ngOnInit(){}

  ngOnDestroy(){}
}

【讨论】：

【解决方案2】：

方法ngOnInit 和ngOnDestroy 应该在构造函数之外。像这样：

// imports ...

@Component({
  // ...
})
export class SubmissionComponent implements OnInit, OnDestroy {
  // ...

  constructor( /* ... */ ) {
    // ...
  }

  ngOnInit() {
    // ...
  }

  ngOnDestroy() {
    // ...
  }
}

【讨论】：