Classes

Classes are basic building blocks in Rio. Each instance of a class represent a data state and set of methods associated with it. You define classes in a file called template.yml. Below is an sample template file defining a Rio class:

init: index.init
getState: index.getState
methods:
  - method: sayHello
    type: WRITE
    handler: index.sayHello

In object oriented approach usually there is a constructor method and other methods. Here we have a init method and list of other methods defined in methods section.

Constructor method is defined in index.init. It's purpose is to initialize the state of this instance when it is first created. An example init method can be something like:

export async function init(data: Data): Promise<Data> {
    data.state.private = { foo: "bar" }
    return data
}

This class has one method called sayHello and it is defined in index.sayHello file.

export async function sayHello(data: Data): Promise<Data> {
    data.state.private.foo = "Hello World" // Set some field on state
    return data
}

An Example Class

Let's think of a simple User class with an updateProfile method:

init: index.init
getState: index.getState
methods:
  - method: updateProfile
    type: WRITE
    handler: index.updateProfile

We can have a separate instance of this class for every single user in our system. There could be millions of instances. Each instance's method can be called and handed it's own state data as it's input. updateProfile method can be like:

export async function updateProfile(data: Data): Promise<Data> {
    data.state.private.firstName = data.request.body.firstName 
    return data
}