title: Sub-dependencies
description: Chain dependencies in JustAPI where one dependency requires another.
keywords: [JustAPI, sub-dependencies, dependency chain, dependency injection]

Chaining Dependencies

Dependencies can depend on other dependencies. JustAPI resolves the entire chain automatically:

from justapi import JustAPIApp, Depends

app = JustAPIApp()

# Level 1: get token from header
def get_token(authorization: str = Header(...)):
    return authorization.replace("Bearer ", "")

# Level 2: decode token to get user
def get_user(token: str = Depends(get_token)):
    # In production, decode JWT
    return {"user_id": 1, "name": "Alice"}

# Level 3: use user in handler
@app.get("/profile")
def profile(user: dict = Depends(get_user)):
    return {"user": user["name"]}

JustAPI resolves get_token → get_user → profile automatically.

Sharing Dependencies

def get_db():
    return DatabaseConnection()

def get_current_user(db: DBSession = Depends(get_db)):
    return db.query_user()

def get_admin_user(user: dict = Depends(get_current_user)):
    if user.get("role") != "admin":
        raise HTTPException(status_code=403)
    return user

See Also

• Classes as Dependencies — class-based deps
• Global Dependencies — app-wide deps