如何修复 Angular Service ngOnInit() 未被调用

问题：

你有一个实现 OnInit 的 Angular 服务：

my-service.ts

import { Injectable, OnInit } from '@angular/core';

@Injectable()
export class MyService implements OnInit {

  constructor() { }

  ngOnInit() {
    console.log("MyService initializing");
  }
}

import { Injectable, OnInit } from '@angular/core';

@Injectable()
export class MyService implements OnInit {

  constructor() { }

  ngOnInit() {
    console.log("MyService initializing");
  }
}

但它从不打印 MyService initializing - 即 ngOnInit() 函数从未被实际调用。

解决方案

服务不应实现 OnInit，该函数故意从不被调用。相反，将 ngOnInit() 中的代码添加到 constructor() 中，并删除 implements OnInit 和 ngOnInit()：

my-service.ts

import { Injectable, OnInit } from '@angular/core';

@Injectable()
export class MyService {

  constructor() {
    console.log("MyService initializing");
  }

}

import { Injectable, OnInit } from '@angular/core';

@Injectable()
export class MyService {

  constructor() {
    console.log("MyService initializing");
  }

}

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