Hooks¶
Hooks allow executing custom code as part of processing a CRUD request. You can use this to validate data, call another custom API, place messages on queues and many other things.
Enabling a hook¶
Define a method, and register it with PiccoloCRUD:
# app.py
from piccolo_api.crud.endpoints import PiccoloCRUD
from movies.tables import Movie
# set movie rating to 10 before saving
async def set_movie_rating_10(row: Movie):
row.rating = 10
return row
# set movie rating to 20 before saving
async def set_movie_rating_20(row: Movie):
row.rating = 20
return row
async def pre_delete(row_id):
pass
# Register one or multiple hooks
app = PiccoloCRUD(
table=Movie,
read_only=False,
hooks=[
Hook(hook_type=HookType.pre_save, callable=set_movie_rating_10),
Hook(hook_type=HookType.pre_save, callable=set_movie_rating_20),
Hook(hook_type=HookType.pre_delete, callable=pre_delete)
]
)
You can specify multiple hooks (also per hook_type). Hooks are executed in order.
You can use either async or regular functions.
Hook types¶
There are different hook types, and each type takes a slightly different set of inputs.
It’s also important to return the expected data from your hook.
pre_save¶
This hook runs during POST requests, prior to inserting data into the database.
It takes a single parameter, row, and should return the row:
async def set_movie_rating_10(row: Movie):
row.rating = 10
return row
app = PiccoloCRUD(table=Movie, read_only=False, hooks=[
Hook(hook_type=HookType.pre_save, callable=set_movie_rating_10)
]
)
pre_patch¶
This hook runs during PATCH requests, prior to changing the specified row in the database.
It takes two parameters, row_id which is the id of the row to be changed,
and values which is a dictionary of incoming values.
Each function must return a dictionary which represent the data to be modified.
async def reset_name(row_id: int, values: dict):
current_db_row = await Movie.objects().get(Movie.id==row_id)
if values.get("name"):
values["name"] = values["name"].replace(" ", "")
return values
app = PiccoloCRUD(
table=Movie,
read_only=False,
hooks=[
Hook(hook_type=HookType.pre_patch, callable=reset_name)
]
)
pre_delete¶
This hook runs during DELETE requests, prior to deleting the specified row in the database.
It takes one parameter, row_id which is the id of the row to be deleted.
pre_delete hooks should not return data.
async def pre_delete(row_id: int):
pass
app = PiccoloCRUD(
table=Movie,
read_only=False,
hooks=[
Hook(hook_type=HookType.pre_delete, callable=pre_delete)
]
)
Dependency injection¶
Each hook can optionally receive the Starlette request object. Just
add request as an argument in your hook, and it’ll be injected automatically.
async def set_movie_rating_10(row: Movie, request: Request):
...