tRPC End-to-End Type Safe APIs · 课时

扩展 tRPC 功能

探索使用自定义构建器、插件以及与其他库集成来扩展 tRPC 的高级方法。

扩展 tRPC 功能 是 CoddyKit 上的免费 tRPC End-to-End Type Safe APIs 课时。这是第 3 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 tRPC End-to-End Type Safe APIs 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 tRPC End-to-End Type Safe APIs 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Extend tRPC's Core

tRPC is incredibly powerful out-of-the-box, but sometimes your application needs more custom control and specialized behavior. This lesson will show you how to extend tRPC beyond basic middleware.

We'll explore custom procedure builders for creating specialized API endpoints and discuss how to integrate tRPC seamlessly with other libraries like ORMs.

Why Custom Builders?

Standard middleware is great for applying common logic to all or a group of procedures, such as authentication or logging.

But what if you need to define specific types of procedures, like adminProcedure or publicProcedure, each with unique context properties or pre-configured middleware chains? Custom procedure builders are perfect for this!

Crafting a Builder with `createBuilder`

tRPC provides the createBuilder utility to help you define your own procedure factory. This builder can extend the context (ctx), add metadata, or apply middleware automatically to any procedure built with it.

It allows you to abstract common setup logic into a reusable pattern, making your API definitions cleaner and more consistent.

Builder Example: Admin Procedure

Let's create an adminProcedure. This builder ensures the user is not only logged in (via protectedProcedure) but also has an isAdmin flag set in their context. This logic is then automatically applied to any procedure using adminProcedure.

// Minimal tRPC-like setup for demonstration
type Context = { user?: { id: number; isAdmin?: boolean } };

const mockProcedure = {
  use: (middleware: any) => ({
    use: (nextMiddleware: any) => ({
      _isBuilder: true,
      _middlewares: [middleware, nextMiddleware]
    }),
    _isBuilder: true,
    _middlewares: [middleware]
  }),
  _isBuilder: true,
  _middlewares: []
};

const t = {
  procedure: mockProcedure
};

// --- Actual tRPC Builder Code ---
const protectedProcedure = t.procedure.use(async ({ ctx, next }: any) => {
  if (!ctx.user) {
    throw new Error('Not authenticated');
  }
  return next({ ctx: { ...ctx, user: ctx.user } });
});

const adminProcedure = protectedProcedure.use(async ({ ctx, next }: any) => {
  if (!ctx.user?.isAdmin) {
    throw new Error('Not an admin!');
  }
  return next({ ctx: { ...ctx, user: ctx.user } });
});

console.log("Protected procedure builder defined.");
console.log("Admin procedure builder defined.");
console.log("Admin procedure has " + adminProcedure._middlewares.length + " middlewares.");

Benefits of Custom Builders

Custom builders offer several significant advantages:

Reusability: Define complex logic once and apply it across many procedures.
Type Safety: Enforce specific context types for groups of procedures.
Readability: Procedures become self-documenting (e.g., adminProcedure.query(...) clearly indicates its requirements).
Consistency: Ensure all procedures of a certain type adhere to specific rules and checks.

Integration with External Libraries

tRPC is unopinionated about your data layer. This means you can easily integrate it with any ORM (like Prisma, Drizzle), database client, or external API service you prefer.

The key to this seamless integration is often to initialize instances of these clients and attach them to your tRPC context. This makes them readily available to all your procedures.

Contextualizing an ORM (Prisma)

A very common pattern in tRPC applications is to initialize your ORM client (e.g., Prisma Client) and then attach that instance to your tRPC context object.

This allows all your tRPC procedures to access the database client via ctx.prisma, centralizing its management and providing type safety.

// Minimal tRPC-like setup for demonstration
type MockPrismaClient = {
  user: {
    findUnique: (args: { where: { id: number } }) => { id: number; name: string } | null;
  };
};

type ContextWithPrisma = {
  prisma: MockPrismaClient;
};

const mockProcedure = {
  query: (handler: (opts: { ctx: ContextWithPrisma }) => any) => ({
    _handler: handler,
    _isQuery: true
  })
};

const t = {
  procedure: mockProcedure
};

// --- Actual tRPC Context Integration ---
const publicProcedure = t.procedure;

const getUserProcedure = publicProcedure.query(async ({ ctx }) => {
  const user = await ctx.prisma.user.findUnique({ where: { id: 1 } });
  return user ? `User name: ${user.name}` : 'User not found.';
});

// --- Demonstration (conceptual execution) ---
const mockPrisma: MockPrismaClient = {
  user: {
    findUnique: (args) => {
      if (args.where.id === 1) {
        return { id: 1, name: 'Alice' };
      }
      return null;
    }
  }
};

const mockContext: ContextWithPrisma = { prisma: mockPrisma };

console.log("Prisma client attached to context type.");
console.log("Conceptual handler output for user 1:");
console.log(await getUserProcedure._handler({ ctx: mockContext }));

The Power of Plugins (Conceptual)

Beyond builders, tRPC offers an experimental createTRPCPlugin API. Plugins provide even deeper hooks into tRPC's internals, allowing you to customize error formatting, add custom data transformers, or modify the request lifecycle in advanced ways.

They are designed for truly complex, core-level extensions that affect how tRPC operates at a foundational level.

When to Use What?

Choosing between custom builders and plugins depends on your extension needs:

Custom Builders: Best for defining specific types of procedures, enriching the context object, or applying common middleware chains. They operate at the procedure definition level.
Plugins: Ideal for modifying tRPC's core behavior, such as custom error handling, data serialization/deserialization, or integrating with external systems at a global, foundational level.

Quick Check

Which of the following are key benefits of using custom tRPC procedure builders?

Summary of Extensions

In this lesson, we explored how to extend tRPC's capabilities. We learned to use custom procedure builders to create specialized, reusable procedures like adminProcedure, enhancing reusability, type safety, and consistency.

We also saw how to integrate external libraries like ORMs by attaching them to the tRPC context. Finally, we touched upon the advanced potential of tRPC plugins for deeper core modifications. These tools empower you to tailor tRPC to your application's unique needs.

常见问题解答

「扩展 tRPC 功能」课时是免费的吗？

是的 — 「扩展 tRPC 功能」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 tRPC End-to-End Type Safe APIs 课程的其余内容，请升级到 CoddyKit PRO。 tRPC End-to-End Type Safe APIs 课程共包含 4 节课。

「扩展 tRPC 功能」这节课中我会学到什么？

探索使用自定义构建器、插件以及与其他库集成来扩展 tRPC 的高级方法。你通过在浏览器中直接运行的动手代码来练习 tRPC End-to-End Type Safe APIs，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 tRPC End-to-End Type Safe APIs 需要有经验吗？

无需任何先前经验。CoddyKit 上的 tRPC End-to-End Type Safe APIs 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 3 节课，共 4 节。

「扩展 tRPC 功能」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 tRPC End-to-End Type Safe APIs 课中编写并运行代码吗？

能。每节 tRPC End-to-End Type Safe APIs 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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