[Solved] You implemented this middleware class:class MyMiddleware: async def dispatch(self, request, call_next): print("Running") response = await call_next(request) return response app = FastAPI() app.... | FastAPI

FastAPI - Middleware and Hooks

You implemented this middleware class:

class MyMiddleware:
    async def dispatch(self, request, call_next):
        print("Running")
        response = await call_next(request)
        return response

app = FastAPI()
app.add_middleware(MyMiddleware)

Why does this middleware never execute when requests are made?

ABecause dispatch method is missing the self parameter

BBecause MyMiddleware does not inherit from a proper middleware base class

CBecause add_middleware requires a function, not a class

DBecause the middleware is added after the app starts

Step-by-Step Solution

Solution:

Step 1: Check middleware class inheritance
FastAPI middleware classes must inherit from Starlette's BaseHTTPMiddleware or similar.
Step 2: Identify missing inheritance
MyMiddleware lacks inheritance, so FastAPI cannot recognize it as middleware.
Final Answer:
Because MyMiddleware does not inherit from a proper middleware base class -> Option B
Quick Check:
Middleware must inherit BaseHTTPMiddleware or similar [OK]

Quick Trick: Middleware classes must inherit BaseHTTPMiddleware [OK]

Common Mistakes:

MISTAKES

Not inheriting from BaseHTTPMiddleware
Incorrect method signatures
Adding middleware after app startup

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You implemented this middleware class:

Step 1: Check middleware class inheritance

Step 2: Identify missing inheritance

Final Answer:

Quick Check:

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