svelte

@json-render/svelte

可将 json-render 规范转换为 Svelte 组件树的 Svelte 5 渲染器。

快速入门

<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>

创建目录

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",
    },
  },
});

定义组件

组件应接受 BaseComponentProps<TProps>：

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
}

<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>

<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>

创建注册表

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
    },
  },
});

规范结构（元素树）

Svelte schema 使用元素树格式：

{
  "root": "card1",
  "elements": {
    "card1": {
      "type": "Card",
      "props": { "title": "Hello" },
      "children": ["btn1"]
    },
    "btn1": {
      "type": "Button",
      "props": { "label": "Click me" }
    }
  }
}

可见性条件

在元素上使用 visible，根据状态显示或隐藏元素：

• { "$state": "/path" } - 检查值是否为真
• { "$state": "/path", "eq": value } - 检查是否相等
• { "$state": "/path", "not": true } - 检查值是否为假
• { "$and": [cond1, cond2] } - AND 条件
• { "$or": [cond1, cond2] } - OR 条件

Providers（通过 JsonUIProvider）

JsonUIProvider 组合所有上下文。各个上下文如下：

上下文	用途
StateContext	在组件之间共享状态（JSON Pointer 路径）
ActionContext	处理通过事件系统分发的操作
VisibilityContext	根据状态启用条件渲染
ValidationContext	表单字段校验

事件系统

组件使用 emit 触发命名事件。元素的 on 字段将事件映射到操作绑定：

<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>

{
  "type": "Button",
  "props": { "label": "Submit" },
  "on": { "press": { "action": "submit" } }
}

内置操作

setState 操作会自动处理并更新状态模型：

{
  "action": "setState",
  "actionParams": { "statePath": "/activeTab", "value": "home" }
}

其他内置操作：pushState、removeState、push、pop。

动态属性和双向绑定

嵌套列表可以在外层 repeat 内将 repeat.statePath 设为 { "$item": "field" }。

组件接收属性前会解析以下表达式形式：

• {"$state": "/state/key"} - 从状态中读取
• {"$bindState": "/form/email"} - 从状态中读取并回写
• {"$bindItem": "field"} - 为 repeat 项读取并回写
• {"$cond": <condition>, "$then": <value>, "$else": <value>} - 条件值

要在组件内使用可写绑定，请使用 getBoundProp：

<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} />

上下文辅助函数

推荐使用的辅助函数：

• getStateValue(path) - 返回 { current }（可读写）
• getBoundProp(() => value, () => bindingPath) - 返回 { current }（绑定时可读写）
• isVisible(condition) - 返回 { current }（布尔值）
• getAction(name) - 返回 { current }（已注册的处理程序）

高级上下文访问：

• getStateContext()
• getActionContext()
• getVisibilityContext()
• getValidationContext()
• getOptionalValidationContext()
• getFieldValidation(ctx, path, config?)

流式 UI

使用 createUIStream 流式传输规范：

<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}

使用 createChatUI 处理聊天和 UI 响应：

const chat = createChatUI({ api: "/api/chat-ui" });
await chat.send("Build a settings panel");