Chaining Decorators

Pyramid has a decorator= argument to its view configuration. It accepts a single decorator that will wrap the mapped view callable represented by the view configuration. That means that, no matter what the signature and return value of the original view callable, the decorated view callable will receive two arguments: context and request and will return a response object:

# the decorator

def decorator(view_callable):
    def inner(context, request):
        return view_callable(context, request)
    return inner

# the view configuration

@view_config(decorator=decorator, renderer='json')
def myview(request):
    return {'a':1}

But the decorator argument only takes a single decorator. What happens if you want to use more than one decorator? You can chain them together:

def combine(*decorators):
    def floo(view_callable):
        for decorator in decorators:
            view_callable = decorator(view_callable)
        return view_callable
    return floo

def decorator1(view_callable):
    def inner(context, request):
        return view_callable(context, request)
    return inner

def decorator2(view_callable):
    def inner(context, request):
        return view_callable(context, request)
    return inner

def decorator3(view_callable):
    def inner(context, request):
        return view_callable(context, request)
    return inner

alldecs = combine(decorator1, decorator2, decorator3)
two_and_three = combine(decorator2, decorator3)
one_and_three = combine(decorator1, decorator3)

@view_config(decorator=alldecs, renderer='json')
def myview(request):
    return {'a':1}