Documento original del Skill
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@json-render/svelte
Svelte 5 renderer that converts json-render specs into Svelte component trees.
Quick Start
svelte
<script lang="ts">
import { Renderer, JsonUIProvider } from "@json-render/svelte";
import type { Spec } from "@json-render/svelte";
import Card from "./components/Card.svelte";
import Button from "./components/Button.svelte";
interface Props {
spec: Spec | null;
}
let { spec }: Props = $props();
const registry = { Card, Button };
</script>
<JsonUIProvider>
<Renderer {spec} {registry} />
</JsonUIProvider>Creating a Catalog
typescript
import { defineCatalog } from "@json-render/core";
import { schema } from "@json-render/svelte";
import { z } from "zod";
export const catalog = defineCatalog(schema, {
components: {
Button: {
props: z.object({
label: z.string(),
variant: z.enum(["primary", "secondary"]).nullable(),
}),
description: "Clickable button",
},
Card: {
props: z.object({ title: z.string() }),
description: "Card container with title",
},
},
});Defining Components
Components should accept BaseComponentProps<TProps>:
typescript
interface BaseComponentProps<TProps> {
props: TProps; // Resolved props for this component
children?: Snippet; // Child elements (use {@render children()})
emit: (event: string) => void; // Fire a named event
bindings?: Record<string, string>; // Map of prop names to state paths (for $bindState)
loading?: boolean; // True while spec is streaming
}svelte
<!-- Button.svelte -->
<script lang="ts">
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ label: string; variant?: string }> {}
let { props, emit }: Props = $props();
</script>
<button class={props.variant} onclick={() => emit("press")}>
{props.label}
</button>svelte
<!-- Card.svelte -->
<script lang="ts">
import type { Snippet } from "svelte";
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ title: string }> {
children?: Snippet;
}
let { props, children }: Props = $props();
</script>
<div class="card">
<h2>{props.title}</h2>
{#if children}
{@render children()}
{/if}
</div>Creating a Registry
typescript
import { defineRegistry } from "@json-render/svelte";
import { catalog } from "./catalog";
import Card from "./components/Card.svelte";
import Button from "./components/Button.svelte";
const { registry, handlers, executeAction } = defineRegistry(catalog, {
components: {
Card,
Button,
},
actions: {
submit: async (params, setState, state) => {
// handle action
},
},
});Spec Structure (Element Tree)
The Svelte schema uses the element tree format:
json
{
"root": "card1",
"elements": {
"card1": {
"type": "Card",
"props": { "title": "Hello" },
"children": ["btn1"]
},
"btn1": {
"type": "Button",
"props": { "label": "Click me" }
}
}
}Visibility Conditions
Use visible on elements to show/hide based on state:
{ "$state": "/path" }- truthy check{ "$state": "/path", "eq": value }- equality check{ "$state": "/path", "not": true }- falsy check{ "$and": [cond1, cond2] }- AND conditions{ "$or": [cond1, cond2] }- OR conditions
Providers (via JsonUIProvider)
JsonUIProvider composes all contexts. Individual contexts:
| Context | Purpose |
|---|---|
StateContext | Share state across components (JSON Pointer paths) |
ActionContext | Handle actions dispatched via the event system |
VisibilityContext | Enable conditional rendering based on state |
ValidationContext | Form field validation |
Event System
Components use emit to fire named events. The element's on field maps events to action bindings:
svelte
<!-- Button.svelte -->
<script lang="ts">
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ label: string }> {}
let { props, emit }: Props = $props();
</script>
<button onclick={() => emit("press")}>{props.label}</button>json
{
"type": "Button",
"props": { "label": "Submit" },
"on": { "press": { "action": "submit" } }
}Built-in Actions
The setState action is handled automatically and updates the state model:
json
{
"action": "setState",
"actionParams": { "statePath": "/activeTab", "value": "home" }
}Other built-in actions: pushState, removeState, push, pop.
Dynamic Props and Two-Way Binding
Nested lists can set repeat.statePath to { "$item": "field" } inside an enclosing repeat.
Expression forms resolved before your component receives props:
{"$state": "/state/key"}- read from state{"$bindState": "/form/email"}- read + write-back to state{"$bindItem": "field"}- read + write-back for repeat items{"$cond": <condition>, "$then": <value>, "$else": <value>}- conditional value
For writable bindings inside components, use getBoundProp:
svelte
<script lang="ts">
import { getBoundProp } from "@json-render/svelte";
import type { BaseComponentProps } from "@json-render/svelte";
interface Props extends BaseComponentProps<{ value?: string }> {}
let { props, bindings }: Props = $props();
let value = getBoundProp<string>(
() => props.value,
() => bindings?.value,
);
</script>
<input bind:value={value.current} />Context Helpers
Preferred helpers:
getStateValue(path)- returns{ current }(read/write)getBoundProp(() => value, () => bindingPath)- returns{ current }(read/write when bound)isVisible(condition)- returns{ current }(boolean)getAction(name)- returns{ current }(registered handler)
Advanced context access:
getStateContext()getActionContext()getVisibilityContext()getValidationContext()getOptionalValidationContext()getFieldValidation(ctx, path, config?)
Streaming UI
Use createUIStream for spec streaming:
svelte
<script lang="ts">
import { createUIStream, Renderer } from "@json-render/svelte";
const stream = createUIStream({
api: "/api/generate-ui",
onComplete: (spec) => console.log("Done", spec),
});
async function generate() {
await stream.send("Create a login form");
}
</script>
<button onclick={generate} disabled={stream.isStreaming}>
{stream.isStreaming ? "Generating..." : "Generate UI"}
</button>
{#if stream.spec}
<Renderer spec={stream.spec} {registry} loading={stream.isStreaming} />
{/if}Use createChatUI for chat + UI responses:
typescript
const chat = createChatUI({ api: "/api/chat-ui" });
await chat.send("Build a settings panel");