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Version: XState v5

@xstate/svelte

The @xstate/svelte package contains utilities for using XState with Svelte.

Templates

Use the following templates to get started quickly with XState and Svelte:

Installation

Install the latest versions of both xstate and @xstate/svelte. xstate is a peer dependency of @xstate/svelte.

npm install xstate @xstate/svelte

API

useMachine(machine, options?)

A function that creates an actor from the given machine and starts an actor that runs for the lifetime of the component.

Arguments

Returns { snapshot, send, actorRef}:

  • snapshot - A Svelte store representing the current state of the machine
  • send - A function that sends events to the running actor ref.
  • actorRef - The created actor ref.

useSelector(actorRef, selector, compare?, getSnapshot?)

A function that returns Svelte store representing the selected value from the snapshot of an actorRef, such as an actor. The store will only be updated when the selected value changes, as determined by the optional compare function.

Arguments

  • actorRef - An actor ref
  • selector - a function that takes in an actor’s current state (snapshot) as an argument and returns the desired selected value.
  • compare (optional) - a function that determines if the current selected value is the same as the previous selected value.

Examples

Coming soon

Matching States

When using hierarchical and parallel machines, the state values will be objects, not strings. In this case, it is best to use state.matches(...).

{#if $state.matches('idle')}
//
{:else if $state.matches({ loading: 'user' })}
//
{:else if $state.matches({ loading: 'friends' })}
//
{/if}

Persisted and Rehydrated State

You can persist and rehydrate state with useMachine(...) via options.snapshot:

// Get the persisted state config object from somewhere, e.g. localStorage
const persistedState = JSON.parse(
localStorage.getItem('some-persisted-state-key'),
);

const { snapshot, send } = useMachine(someMachine, {
snapshot: persistedState,
});

// state will initially be that persisted state, not the machine’s initialState