Thomas N. Thomas N. - 7 months ago 13
Python Question

Flask decorator : Can't pass a parameter from URL

i'm quite new with flask and i'm trying to use the migthy power of decorators :p
I read lot of things and found tons of topics about python decorators here but nothing really helpful.

@app.route('groups/<id_group>')
@group_required(id_group)
@login_required
def groups_groupIndex(id_group):
#do some stuff
return render_template('index_group.html')


This is the error i get :

@group_required(id_group), NameError: name 'id_group' is not defined


Ok, id_group is not defined yet, but I don't understand why i CAN use the id_group parameter from the URL in the function groups_groupIndex but NOT in the decorator!

I try to move/switch decorators, but the same error occure each time.

Here is my decorator, but it seems to work fine

def group_required(group_id):
def decorated(func):
@wraps(func)
def inner (*args, **kwargs):
#Core_usergroup : table to match users and groups
groups = Core_usergroup.query.filter_by(user_id = g.user.id).all()
for group in groups:
#if the current user is in the group : return func
if int(group.group_id) == int(group_id) :
return func(*args, **kwargs)
flash(gettext('You have no right on this group'))
return render_template('access_denied.html')
return inner
return decorated


Maybe i don't see decorators like i should... Can i use my decorator this way or need i rewrite something different ?

Answer

You defined group_id as a function parameter; that makes it a local name in that function.

That doesn't make the name available to other scopes; the global namespace that the decorator lives in cannot see that name.

The wrapper function, however, can. It'll be passed that parameter from the @apps.route() wrapper when called:

def group_required():
    @wraps(func)
    def wrapper(group_id, *args, **kwargs):
        #Core_usergroup : table to match users and groups
        groups = Core_usergroup.query.filter_by(user_id = g.user.id).all()
        for group in groups:
            #if the current user is in the group : return func
            if int(group.group_id) == int(group_id) :
                return func(*args, **kwargs)
        flash(gettext('You have no right on this group'))
        return render_template('access_denied.html')     
    return wrapper
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