请求上下文模式

import { Provide } from '@midwayjs/decorator';
import { writeFileSync, readFileSync, existsSync } from 'fs';
const filePath = './todo';
@Provide('TodoListService')
export class TodoListService {
  todoList = [];
  // 等价于，每次都会创建一个新的实例
  constructor() {
      this.todoList = []
  }
  list() {
    if (existsSync(filePath)) {
      const buffer = readFileSync(filePath);
      this.todoList = JSON.parse(buffer.toString());
    }
    return this.todoList;
  }
}

单例模式

import { Provide, Scope, ScopeEnum } from '@midwayjs/decorator';
import { writeFileSync, readFileSync, existsSync } from 'fs';
const filePath = './todo';
@Scope(ScopeEnum.Singleton) // 单例模式
@Provide('TodoListService')
export class TodoListService {
  private todoList = [];
  list() {
    if (existsSync(filePath)) {
      const buffer = readFileSync(filePath);
      this.todoList = JSON.parse(buffer.toString());
    }
    return this.todoList;
  }
}