🔒 decorator wrapper function

[glacial geode]

@lime dagger

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[zealous kelp]

because decorators return callables

we need to define the inner function so we have a callable to return

we don't usually care about the nested function outside the scope of the decorator function, so it makes sense to define it within

[fervent cove]

your code doesn't work if you try to call hello_world() again

try it

I misspoke

[zealous kelp]

yes

we don't want to call the function when we wrap it

[fervent cove]

that is what the @decorator_function syntax would do

the latter snippet is not decorating anything

[zealous kelp]

def decorator_function(func):
    def wrapper():
        print("I have decorated the function")
        func()
        
    return wrapper
    
def hello_world():
    print("Hello world")
    
decorator_function(hello_world)

notice how we don't get Hello World printed here

!e

def decorator_function(func):
    print("I have decorated the function")
    func()
    
def hello_world():
    print("Hello world")
    
decorator_function(hello_world)

[glacial geode]

:white_check_mark: Your 3.13 eval job has completed with return code 0.

001 | I have decorated the function
002 | Hello world

[zealous kelp]

but we do here

This is a problem (and clearly different behaviour). We want the returned callable.

decorators let us modify how a function is called without changing the body of the actual function

if we think of functions as boxes that we open, a decorator is putting our box inside another box and then we open the outer box first before opening the inner box

this is useful if for example we wanted a decorator that makes a function requires a user to be logged in so they can perform an action

def require_login(f):
    def wrapper():
        if user_logged_in:
            f()
        else:
            raise RuntimeError("User is not logged in")


@require_login
def check_inbox():
    ...

yes exactly

I work with 3d software and a common one I use is to treat a single function as one "undo chunk"

so I can group a bunch of actions together but if the user presses undo, it will go back to the start instead of undoing each individual action

def undo_chunk(f):
    def wrapper():
        cmds.undoInfo(openChunk=True)
        f()
        cmds.undoInfo(closeChunk=True)


@undo_chunk
def do_lots_of_stuff():
    ...

np!

[glacial geode]

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