採用async方式獲取數據庫中的數據，返回的是一個Promise<T>。直接在模板中去解析Promise得到的會是一個Promise對象，而不是最終返回的結果，然後用{{message.name}}去解析是會失敗的。
解決方法，所有async方法配套加上await。拿一個官網的例子。
https://docs.nestjs.com/providers
cats.controller.ts
import { Controller, Get, Post, Body } from '@nestjs/common';
import { CreateCatDto } from './dto/create-cat.dto';
import { CatsService } from './cats.service';
import { Cat } from './interfaces/cat.interface';
@Controller('cats')
export class CatsController {
constructor(private readonly catsService: CatsService) {}
@Post()
async create(@Body() createCatDto: CreateCatDto) {
this.catsService.create(createCatDto);
}
@Get()
async findAll(): Promise<Cat[]> {
return await this.catsService.findAll(); // 官網demo沒有添加await關鍵詞
}
}
一個真實小項目的例子
crashes.controller.ts
import { Controller, Get, Post, Body, Param, Render, Res } from '@nestjs/common';
import { CreateCrashDto } from './dto/create-Crash.dto';
import { CrashesService } from './crashes.service';
import { Response } from 'express';
import { Crash } from './interfaces/crashes.interface';
@Controller('Crashes')
export class CrashesController {
constructor(private readonly crashesService: CrashesService) { }
@Get('/:version/:user')
@Render('index')
async findVersionUser(@Param('version') version: string, @Param('user') user: string): Promise<any> {
let result = await this.crashesService.aggregateVersionAsync(version);
let total = await this.crashesService.aggregateVersionCountAsync(version);
return { message: result, total: total.length };
}
}
index.hbs
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>App</title>
</head>
<p> group count :{{ message.length}}</p>
<body>
<table border="1">
<td>tip</td>
<td>count</td>
{{#each message}}
<tr>
<td><a href="/crashes/{{_id}}">{{_id}} </a> </td>
<td> {{num}} </td>
</tr>
{{/each}}
</table>
</body>
</html>
crashes.service.ts
import { Inject, Injectable } from '@nestjs/common';
import { Model } from 'mongoose';
import { CreateCrashDto } from './dto/create-crash.dto';
import { Crash } from './interfaces/crashes.interface';
@Injectable()
export class CrashesService {
constructor(@Inject('Crash_MODEL') private readonly CrashModel: Model<Crash>) { }
async aggregateVersionCountAsync(version: string): Promise<Crash[]> {
return await this.CrashModel.aggregate([{ $match: { version } }]);
}
async aggregateVersionAsync(version: string): Promise<Crash[]> {
return await this.CrashModel.aggregate([{ $match: { version } },
{ $group: { _id: '$tip', num: { $sum: 1 }, crashes: { $push: '$_id' } } },
{ $sort: { num: -1 } }]).exec();
}
async findAllVersion(): Promise<Crash[]> {
return await this.CrashModel.aggregate([
{ $match: { _id: { $ne: '-1' }, version: { $ne: '' } } },
{ $group: { _id: '$version', num: { $sum: 1 } } },
{ $sort: { _id: -1 } }]).exec();
}
}