DEV Community: Andre Carstens

Create npm api project with nest

Andre Carstens — Fri, 21 Apr 2023 16:02:53 +0000

To build a new backend api that you can host in AWS Lambda or Azure app services, you can start with a blank node project. You should just install nest - npm -install nest

When nest is installed, call the cli and it will scaffold a project for you.

npx @nest/cli new project-name

nest will create the src folder for you, it will setup a controller, a module, a test and a service. It will also create main.js and assign port 3000 as your default. You can access the app on port 3000 immediately.

Adding swagger

install swagger from the terminal
npm install --save @nestjs/swagger

in main.js, import swagger
import { DocumentBuilder,SwaggerModule } from '@nestjs/swagger';

Then you setup swagger details using options and then render it to /api using app as a parameter.

const options = new DocumentBuilder()
.setTitle('My API')
.setDescription('My API description')
.setVersion('1.0')
.build();

const document =SwaggerModule.createDocument(app,options);
SwaggerModule.setup('api',app,document);

How to Moq ILogger for .net core unit test

Andre Carstens — Tue, 14 Mar 2023 10:21:33 +0000

Using Moq, you can create custom implemenation of your service layers. But what about the standard items we inject into classes such as logging or configuration.

To mock an instance of Microsoft.Extensions.Logging so you can pass it to your underlying class, you create an Mock of ILogger and inject it.

var logger = Mock.Of>();
var xXXXProvider = new XXXXProvider(httpClient,logger,null);

Where the XXXXProvider class has _logger injected into it and you cannot just mock it up.

Asp.Net core SPA proxy wont start

Andre Carstens — Wed, 08 Feb 2023 15:04:21 +0000

When I was trying to start an existing .net core 6 project that has a React SPA embedded in it, I was getting an error that the proxy server was not responding. I spent a lot of time trying to find out where the proxy port is declared, people said its in the package.json file or in launch.settings. I didnt find the port, but I did find out that the proxy spa feature of .net core looks for an avaialble port to forward to, so it isnt from a setting file.

Anyway, even after finding this out, it made no difference, the SPA app wouldnt start. I tried changing the startup.cs settings
for the SPA.

if (env.IsDevelopment())
spa.UseProxyToSpaDevelopmentServer("http://localhost:xxx")

}
I went from using spa.UseReactDevelopmentServer to spa.UseProxyToSpaDevelopmentServer("http://localhost:"). It didnt help.

Eventually, I tried using a cmd line in the Clientapp\ folder to get npm to start the app.

`npm start

npm threw an error ERR_OSSL_EVP_UNSUPPORTED.`

This was related to an update made to node that moved them from OpenSSL 1.x to OpenSSL 3.x

Eventually, I added the script below to the package.json, and the project finally started working again.

   "start": "rimraf ./build && react-scripts --openssl-legacy-provider start",

C# arrays using Distinct

Andre Carstens — Fri, 03 Feb 2023 09:55:11 +0000

int[] nums = new int[] { 1, 4, 5, 2, 3, 5, 6 };
//unique values
var unique = nums.Distinct();

There is a array of integers as an example above. The Distinct() command will shorten the integer array by removing any duplicate values and returning a shortened array. The duplicate value (5) will be removed and the resulting array will be {1, 4, 2, 3, 5, 6}

Note: The array will not be sorted yet, only the duplicate values removed. To sort the array, you can chain a call to OrderBy() at the end of Distinct().

Question:
Can you specify which values in an integer array, you want to apply Distinct to?

var selectedDistinct = nums.Where(x => x >= 3).Select(x => x).Distinct();

The code above will shorten nums to only values that are greater or equal to 3 and then apply Distinct() to that shortened result.

C# arrays using Average

Andre Carstens — Fri, 03 Feb 2023 08:56:32 +0000

Average is used to get the average of all values within an array.
For example, you can get the average value of all the items in the integer array by using average

int[] nums = new int[] { 1, 4, 5, 2, 3, 5, 6 };

//normal array average
var average = nums.Average();

This will return a double with the value of: 3.7142857142857144

Question:

Can you use a select to filter the items used in average of an array?
Lets try

var averageSelected = nums.Where(x => x >= 2).Select(x => x).Average();

In the code above, the integer array nums is first trimmed using the .Where clause, the .Select clause will choose the value of the array and the .Average() will return the average of the selected values that matched the .Where statement.