Course: "NestJS: The Complete Developer's Guide" by Stephen Grider.
App goal: Store and receive messages (strings) stored in a plain JSON file.
Create a module:
nest generate module messages
Generate a controller (set of) files:
nest generate controller messages/messages --flat
Instead of using postman, you can use the "VScode rest client" extension (iif you are using VScode editor).
- Install this extension from VScode extensions inside the VScode editor.
- Create a file called request.http in the root of your project, and add simple e.g. get and post requests such as the one in the code block below inside it.
- Start your dev server in thhe terminal as usual, test that the code in your controller is working by clicking the "send request" button in the request.http file.
### List all messages
GET http://localhost:3000/messages
### Create a new message
POST http://localhost:3000/messages
content-type: application/json
{
"content": "hi there"
}
### Get a particular message
GET http://localhost:3000/messages/123123123
Install two packages for use:
- class-validator
- class-transformer
The example is designed in such a way that you have to:
- Create a messages.json file in the root of the project to avoid errors.
- Also add an empty object
{}in the messages.json file after creating the file so that JSON code can work properly.
This principle states that: A class should not create instances of its dependencies on its own. The down side is that we may need to write many classes and or lines of code. This is not so scalable when the application grows much bigger.
Dependency injection is all about making use of the inversion of control principle but not having to create a ton of different classes or instances every single time we want a controller. We don't have to worry about creating such dependencies ourselves - the dependency injection container/injector takes care of this.