`BaseDetailView` and `SingleObjectMixin` optimization.

[Davit Gachechiladze]

Hi. In BaseDetailView.get(self, request, *args, **kwargs), we have line like context = self.get_context_data(object=self.object). Why should we pass object=self.object ? It's redundant (IMHO).

class SingleObjectMixin(ContextMixin):

    def get_context_data(self, **kwargs):
        """Insert the single object into the context dict."""
        context = {}
        if self.object:
            context['object'] = self.object
            context_object_name = self.get_context_object_name(self.object)
            if context_object_name:
                context[context_object_name] = self.object
        context.update(kwargs)
        return super().get_context_data(**context)

class BaseDetailView(SingleObjectMixin, View):
    """A base view for displaying a single object."""
    def get(self, request, *args, **kwargs):
        self.object = self.get_object()
        context = self.get_context_data(object=self.object)
        return self.render_to_response(context)

I think, it's better idea to implement SingleObjectMixin.get_context_data(self, **kwargs) and BaseDetailView.get(self, request, *args, **kwargs) like this. Code below

class SingleObjectMixin(ContextMixin):
    def get_context_data(self, *, object=None, **kwargs):
        """Insert the single object into the context dict."""
        object = object if object is not None else self.object
        context = {}
        if object:
            context['object'] = object
            context_object_name = self.get_context_object_name(object)
            if context_object_name:
                context[context_object_name] = object
        context.update(kwargs)
        return super().get_context_data(**context)

class BaseDetailView(SingleObjectMixin, View):
    """A base view for displaying a single object."""
    def get(self, request, *args, **kwargs):
        self.object = self.get_object()
        context = self.get_context_data()
        return self.render_to_response(context)

Also, SingleObjectMixin.get_context_data(self, *, object=None, **kwargs) will be implemented in a same fashion as MultipleObjectMixin.get_context_data(self, *, object_list=None, **kwargs) is this moment.

​https://github.com/django/django/pull/11657

[Mariusz Felisiak]

Davit please don't update ticket description so many times, you can refer PR in a comment.

[Davit Gachechiladze]

Replying to felixxm:

Davit please don't update ticket description so many times, you can refer PR in a comment.

Thank you. I will try to do everything better in future.

[Carlton Gibson]

Hi Davit,

Thanks for the suggestion. Strictly you're right, in theory this simplification is available. We can't make it, however.

Firstly, they'll be plenty of folks that overrode get_context_data() relying on the fact that self.object is injected.
(We change it, we break their code.)

Then, removing relies too much on internal knowledge of the CBV implementations.

The general pattern for get_context_data() is this:

def get_context_data(self, **kwargs):
    context = {
        # Some stuff...
    }
    
    # Allow caller to inject the values we want...
    context.update(kwargs)

    return context

Without looking at SingleObjectMixin at all, the implementation of BaseDetailView.get() is exactly what one want's: we want the calling function to drive `get_context_data() by passing in the object to be rendered.

I don't know if you've seen them but check out ​http://django-vanilla-views.org/ for a stripped back take on GCBVs here.

[Davit Gachechiladze]

Replying to Carlton Gibson:

Hi Davit,

Thanks for the suggestion. Strictly you're right, in theory this simplification is available. We can't make it, however.

Firstly, they'll be plenty of folks that overrode get_context_data() relying on the fact that self.object is injected.
(We change it, we break their code.)

Then, removing relies too much on internal knowledge of the CBV implementations.

The general pattern for get_context_data() is this:

def get_context_data(self, **kwargs):
    context = {
        # Some stuff...
    }
    
    # Allow caller to inject the values we want...
    context.update(kwargs)

    return context

Without looking at SingleObjectMixin at all, the implementation of BaseDetailView.get() is exactly what one wants: we want the calling function to drive `get_context_data() by passing in the object to be rendered.

I don't know if you've seen them but check out ​http://django-vanilla-views.org/ for a stripped back take on GCBVs here.

Thank you for explanation.