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Step 4: Define an entity

The routes you learned about in the previous step give you flexibility to implement any behavior you want for client HTTP requests. However, for reading and writing application data, ChiselStrike provides an easy way to build an API that performs CRUD (Create, Read, Update, Delete) operations on entities you define. The only thing you are required to do is write TypeScript classes to express your data model.

Here is code for a sample entity:

my-backend/models/BlogPost.ts
import { ChiselEntity } from "@chiselstrike/api"

export class BlogPost extends ChiselEntity {
    author: string = "Anonymous"
    content: string
    publishedAt: number
    hidden: boolean
}

In your ChiselStrike project, create a new file in the existing models directory and call it BlogPost.ts. Copy the above code into it and save the file. Upon saving the file, chiseld will automatically restart and pick up the new entity. You can verify this in its output:

Applied:
  1 models

Let's break down some of the details of what you see here.

@chiselstrike/api module​

This nodejs module exports the API used to define and operate the backend services provided by ChiselStrike. In this sample, you are only using ChiselEntity to define a single entity.

ChiselEntity​

This is the base class for all entities that you define. ChiselEntity provides a number of functions for working with the entity programmatically. Later in this tutorial, you will see how ChiselStrike can automatically generate a CRUD API using the definition of an entity.

export class BlogPost​

You must export any ChiselEntity classes from TypeScript source files in the models directory in order for ChiselStrike to recognize and work with them.

Property types​

This example uses three different types of properties, which are standard primitive TypeScript string, number, and boolean. ChiselStrike also allows arrays of these types.

Default values​

The author property defines a default value of "Anonymous". This value will be used by ChiselStrike when adding an instance of this entity when no value was provided. ChiselStrike also allows TypeScript optional properties for fields that don't require a value at all.