FastAPI Integration

• Deep Integration

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  Inject anywhere in the request path, not just route handlers, without manually threading dependencies through each call.

  Learn more

• Zero Runtime Overhead

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  Inject dependencies with zero runtime overhead using Class-Based Handlers.

  Learn more

• Background Tasks

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  Inject dependencies into scheduled background callbacks via WireupTask.

  Learn more

• Framework-Agnostic

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  Share your service layer with CLI tools, background workers, and other frameworks.

Migrating from FastAPI Depends?

Evaluating Wireup for your FastAPI project? Check out the migration page which includes common pain points with FastAPI Depends and how to solve them with Wireup as well as a low-friction migration path:

Migrate from FastAPI Depends to Wireup.

Quick Start

This is the shortest path to a working FastAPI endpoint with Wireup injection.

main.py

from fastapi import FastAPI
import wireup
import wireup.integration.fastapi
from wireup import Injected, injectable


# 1. Define services
@injectable
class GreeterService:
    def greet(self, name: str) -> str:
        return f"Hello, {name}!"


# 2. Create container
container = wireup.create_async_container(injectables=[GreeterService])

app = FastAPI()


# 3. Use Injected[T] in routes for Wireup injection
@app.get("/")
async def greet(greeter: Injected[GreeterService]):
    return {"message": greeter.greet("World")}


# 4. Initialize Wireup integration
wireup.integration.fastapi.setup(container, app)

Best practice is to call setup(...) after routes are added.

Run the server with:

fastapi dev main.py

Detailed Guides

• Inject in Routes: HTTP/WebSocket handler injection and config value injection in route signatures.
• Request and WebSocket Context in Services: inject fastapi.Request and fastapi.WebSocket into Wireup services.
• Class-Based Handlers: zero per-request constructor resolution and WireupRoute optimizations.
• Request-Time Injection: injection in decorators, middleware, and other request-time call sites.
• Background Tasks: inject dependencies into scheduled callbacks with WireupTask.
• FastAPI Testing: TestClient lifespan usage, overrides, and request-lifecycle tests.
• Troubleshooting: common setup/runtime errors and fast fixes.

API Reference

• fastapi_integration