classy-solid

Tools for class-based reactivity powered by Solid.js, and for using classes as Solid components (f.e. in a JSX template).

npm install classy-solid --save

API and Usage

Note, these docs assume you have basic knowledge of Solid.js first.

@reactive

Mark a class with this decorator if it will have reactive properties (properties backed by Solid signals). See @signal below for an example.

@signal

Decorate a property of a class with @signal to make it reactive (backed by a Solid signal). Be sure to decorate a class that has reactive properties with the @reactive decorator as well.

import {reactive, signal} from 'classy-solid'
import {createEffect} from 'solid-js'

@reactive
class Car {
	@signal engineOn = false
	@signal sound = 'vroom'
}

const car = new Car()

// ...

createEffect(() => {
	// This re-runs when car.engineOn or car.sound change.
	if (car.engineOn) console.log(car.sound)
})

@component

A decorator for using classes as Solid components.

Note, the @component decorator is still being refined, subject to change in the next few releases.

Examples:

Plain JS

import {component, reactive, signal} from 'classy-solid'

@component
@reactive
class MyComp {
	@signal last = 'none'

	onMount() {
		console.log('mounted')
	}

	template(props) {
		// here we use `props` passed in, or the signal on `this` which is also
		// treated as a prop
		return (
			<h1>
				Hello, my name is {props.first} {this.last}
			</h1>
		)
	}
}

render(() => <MyComp first="Joe" last="Pea" />, document.body)

Note: You only need the @reactive decorator if you will use @signal properties in your class. Make sure the @component decorator comes before the @reactive decorator, or else a runtime error will let you know. :)

Without decorators, for plain JS users who don't have decorator setups in their build yet (note, the new decorators proposal reached stage 3! So this will change soon!):

import {component, reactive, signal} from 'classy-solid'

const MyComp = component(
	reactive(
		class MyComp {
			static signalProperties = ['last']

			last = 'none'

			onMount() {
				console.log('mounted')
			}

			template(props) {
				// here we use `props` passed in, or the signal on `this` which
				// is also a prop on the outside.
				return (
					<h1>
						Hello, my name is {props.first} {this.last}
					</h1>
				)
			}
		},
	),
)

render(() => <MyComp first="Joe" last="Pea" />, document.body)

TypeScript

import {component, reactive, signal, Props} from 'classy-solid'

@component
@reactive
class MyComp {
	// This defines prop types for JSX. Note, this property does not actually
	// need to exist at runtime, hence the `!` to tell TS not to worry about it
	// being undefined.
	PropTypes!: Props<this, 'last' | 'count' | 'first'>

	@signal last = 'none'
	@signal first = 'none'
	@signal count = 123

	// This property will not appear in the JSX prop types, because we did not
	// list it in the PropTypes definition.
	foo = 'blah'

	onMount() {
		console.log('mounted')
	}

	template(props: this['PropTypes']) {
		// Note, unlike the plain JS example, we had to define a `first`
		// property on the class, or else it would not have a type definition
		// here. Plain JS has no types, so no issue there.
		return (
			<h1>
				Hello, my name is {props.first} {this.last}. The count is {this.count}
			</h1>
		)
	}
}

render(() => <MyComp first="Joe" last="Pea" count={456} />, document.body)

If you're using TypeScript syntax, there's no reason not to use decorators because TS has support for it.

createSignalObject()

Returns a Solid signal in the form of an object with .get and .set methods, instead of an array tuple.

let count = createSignalObject(0) // count starts at 0
count.set(1) // set the value of count to 1
count.set(count.get() + 1) // add 1
let currentValue = count.get() // read the current value

In cases where decorators are not yet supported or undesired, using Solid's createSignal directly as a class property is not so ideal:

class Counter {
	count = createSignal(0)

	increment() {
		// These are not so readable:
		this.count[1](this.count[0]() + 1)
		// or
		this.count[1](c => c + 1)
	}
}

createSignalObject provides an alternative that is more usable as a class property:

class Counter {
	count = createSignalObject(0)

	increment() {
		// These are more readable:
		this.count.set(this.count.get() + 1)
		// or
		this.count.set(c => c + 1)
	}
}

createSignalFunction()

Returns a Solid signal in the form of a single overloaded function for both getting and setting the signal, instead of an array tuple. Call the function with no arguments to get the signal value, and call it with an arg to set the signal value.

let count = createSignalFunction(0) // count starts at 0
count(1) // set the value of count to 1
count(count() + 1) // add 1
let currentValue = count() // read the current value

In cases where decorators are not yet supported or undesired, using Solid's createSignal directly as a class property is not so ideal:

class Counter {
	count = createSignal(0)

	increment() {
		// These are not so readable:
		this.count[1](this.count[0]() + 1)
		// or
		this.count[1](c => c + 1)
	}
}

createSignalFunction provides an alternative that is more usable as a class property:

class Counter {
	count = createSignalFunction(0)

	increment() {
		// These are more readable:
		this.count(this.count() + 1)
		// or
		this.count(c => c + 1)
	}
}

signalify()

Use this to convert properties on an object into Solid signal-backed properties.

There are two ways to use this: either by defining which properties to convert to signal-backed properties by providing an array as property names in the second arg, which is useful on plain objects, or by passing in this and this.constructor within the constructor of a class that has reactive properties listed in a static signalProperties array (this is what the @reactive and @signal decorators end up doing behind the scenes).

This can be useful with plain objects, as well with classes in situations where decorators are unavailable or undesired.

In some cases, using signalify is more desirable than Solid's createMutable because the original object will be in use, rather than a Proxy. This can be useful, for example, for patching 3rd-party objects to make them reactive, whereas it would not be possible with createMutable.

Here are some examples. Make certain properties on an object reactive signal-backed properties:

import {signalify} from 'class-solid'
import {createEffect} from 'solid-js'

const obj = {
	foo: 1,
	bar: 2,
	baz: 3,
}

// Make only the 'foo' and 'bar' properties reactive (backed by Solid signals).
signalify(obj, ['foo', 'bar'])

// ...

createEffect(() => {
	console.log(obj.foo, obj.bar)
})

Note, it returns the same object passed in, so you can write this:

const obj = signalify(
	{
		foo: 1,
		bar: 2,
		baz: 3,
	},
	// Make only the 'foo' and 'bar' properties reactive (backed by Solid signals).
	['foo', 'bar'],
)

If you want to make all properties signal-backed, then omitting the array will internally use Object.keys(obj) as a default:

// Make all properties reactive signals
const obj = signalify({
	foo: 1,
	bar: 2,
	baz: 3,
})

Note that the object passed in is the same object returned:

let test
const obj = signalify(test = {...})
console.log(obj === test) // true

Signalify certain properties in a class (alternative to decorators):

import {signalify} from 'class-solid'
import {createEffect} from 'solid-js'

class Counter {
	count = 0
	on = true

	constructor() {
		// Make only the 'count' variable reactive (signal-backed). The 'on'
		// variable remains a regular property.
		signalify(this, ['count'])
	}
}

const c = new Counter()

// ...

createEffect(() => {
	console.log(c.count)
})

The downside of the previous example (namely, not using decorators) is that the code is less DRY, we had to repeat ourselves by writing the word "count" twice. But, if you're okay with it, you can make all properties reactive by omitting the second arg (sometimes you don't want all properties to be reactive):

class Counter {
	count = 0
	on = true

	constructor() {
		// Both 'count' and 'on' will be signal-backed:
		signalify(this)
	}
}

Another way to describe which properties are reactive is with a static signalProperties array and passing the constructor to signalify, which is exactly what the decorators are syntax sugar for:

class Counter {
	count = 0
	on = true

	static signalProperties = ['count']

	constructor() {
		// Only 'count' will be signal-backed:
		signalify(this, this.constructor)
	}
}

Note how with decorators, the code is more DRY and concise, because we don't have to repeat the count word twice, therefore reducing some surface area for human mistakes, and we don't have to write a constructor:

@reactive
class Counter {
	@signal count = 0
	on = true
}