如何使用 MongoDB 数据源在 LoopBack 4 中增加计数器变量? [英] How can I increment a counter variable in LoopBack 4 with a MongoDB datasource?

问题描述

我正在尝试将我的 Nodejs Express 应用程序转换为 Loopback 4，但我不知道如何增加计数器.在我的 Angular 9 应用程序中，当用户单击图标时，计数器会增加.这在 Express 中完美运行

I'm trying to convert my Nodejs Express app to Loopback 4 and I can't figure out how to increment a counter. In my Angular 9 app when a user clicks an icon a counter is incremented. This works perfectly in Express

快递中

const updateIconCount = async function (dataset, collection = 'icons') {
    let query = { _id: new ObjectId(dataset.id), userId: dataset.userId };
    return await mongoController.update(
        collection,
        query,
        { $inc: { counter: 1 } },
        function (err, res) {
            logAccess(res, 'debug', true, 'function update updateIconLink');
            if (err) {
                return false;
            } else {
                return true;
            }
        }
    );
};

我尝试先获取 counter 的值，然后递增，但每次我保存 VS Code 时，都会以一种不寻常的方式重新格式化代码.在这个片段中，我注释掉了导致这种重新格式化的代码行.我可以设置计数器值，例如100.

I tried to first get the value of counter and then increment but every time I save VS Code reformats the code in an an unusual way. In this snippet I commented out the line of code that causes this reformatting. I can set the counter value, e.g. 100.

在环回 4

@patch('/icons/count/{id}', {
    responses: {
      '204': {
        description: 'Icons PATCH success',
      },
    },
  })
  async incrementCountById(
    @param.path.string('id') id: string,
    @requestBody({
      content: {
        'application/json': {
          schema: getModelSchemaRef(Icons, {partial: true}),
        },
      },
    })
    icons: Icons,
  ): Promise<void> {
    // let targetIcon = this.findById(id).then(icon => {return icon});
    icons.counter = 100;
    console.log(icons.counter);
    await this.iconsRepository.updateById(id, icons);
  }

如何在 Loopback 4 中实现 { $inc: { counter: 1 } } ?

How do I implement { $inc: { counter: 1 } } in Loopback 4?

添加到辅助解决方案我的 mongo.datasource.ts

import {inject, lifeCycleObserver, LifeCycleObserver} from '@loopback/core';
import {juggler} from '@loopback/repository';

const config = {
  name: 'mongo',
  connector: 'mongodb',
  url: '',
  host: '192.168.253.53',
  port: 32813,
  user: '',
  password: '',
  database: 'firstgame',
  useNewUrlParser: true,
  allowExtendedOperators: true,
};

// Observe application's life cycle to disconnect the datasource when
// application is stopped. This allows the application to be shut down
// gracefully. The `stop()` method is inherited from `juggler.DataSource`.
// Learn more at https://loopback.io/doc/en/lb4/Life-cycle.html
@lifeCycleObserver('datasource')
export class MongoDataSource extends juggler.DataSource
  implements LifeCycleObserver {
  static dataSourceName = 'mongo';
  static readonly defaultConfig = config;

  constructor(
    @inject('datasources.config.mongo', {optional: true})
    dsConfig: object = config,
  ) {
    super(dsConfig);
  }
}

修正端点

@patch('/icons/count/{id}', {
    responses: {
      '204': {
        description: 'Icons PATCH success',
      },
    },
  })
  async incrementCountById(
    @param.path.string('id') id: string,
    @requestBody({
      content: {
        'application/json': {
          schema: getModelSchemaRef(Icons, {partial: true}),
        },
      },
    })
    icons: Icons,
  ): Promise<void> {
    console.log(id);
    // @ts-ignore
    await this.iconsRepository.updateById(id, {$inc: {counter: 1}});//this line fails
    // icons.counter = 101; //these lines will set the icon counter to 101 so I know it is connecting to the mongodb
    // await this.iconsRepository.updateById(id, icons);
  }

推荐答案

你可以使用 mongo 更新运算符.

You can use the mongo update-operators.

基本上，您只需在 MongoDB 数据源定义中设置 allowExtendedOperators=true (指南).之后就可以直接使用这些运算符了.

Basically, you just have to set allowExtendedOperators=true at your MongoDB datasource definition (guide). After that, you can directly use these operators.

使用示例:

// increment icon.counter by 3
await this.iconsRepository.updateById(id, {$inc: {counter: 3}} as Partial<Counter>);

目前，lb4 类型中缺少这些运算符，因此您必须欺骗打字稿才能接受它们.这很丑陋，但这是我现在能找到的唯一解决方案.

Currently, these operators are missing from the lb4 types so you must cheat typescript to accept them. It's ugly but that's the only solution I could find right now.

你可以关注这个问题看看发生了什么这些运算符.

You can follow this issue to see what's going on with these operators.

这篇关于如何使用 MongoDB 数据源在 LoopBack 4 中增加计数器变量?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！