Refactoring Examples

Real-world code transformations powered by research-backed patterns

Eliminate duplication

Extract repeated logic into reusable components, reducing code size and improving maintainability

players/views.py

-18 lines+11 linesExtract Mixin

BEFORE

Auth logic mixed with business logic

24  @method_decorator(login_required, name='dispatch')
29    class AdminManageUsersView(View):
30      def get(self, request, *args, **kwargs):
31        # Check if the current user is an admin
32        try:
33          player = Player.objects.get(user=request.user)
34          if not player.is_admin:
35            return HttpResponseForbidden("...")
36        except Player.DoesNotExist:
37          return HttpResponseForbidden("...")

x2 DUPLICATED

38        # Get all users...
...
52    def post(self, request, *args, **kwargs):
53      # Check if the current user is an admin
54      try:
55        player = Player.objects.get(user=request.user)
56        if not player.is_admin:
57          return HttpResponseForbidden("...")
58      except Player.DoesNotExist:
59        return HttpResponseForbidden("...")
61      # Handle user deletion...

AFTER

Auth logic cleanly separated

10  class AdminRequiredMixin(LoginRequiredMixin):
11    """Mixin to require admin status."""
13    def dispatch(self, request, *args, **kwargs):
14      try:
15        player = Player.objects.get(user=request.user)
16      except Player.DoesNotExist:
17        return HttpResponseForbidden("...")
19      if not player.is_admin:
20        return HttpResponseForbidden("...")
21      return super().dispatch(request, *args, **kwargs)
...
38  class AdminManageUsersView(AdminRequiredMixin, View):
42    def get(self, request, *args, **kwargs):
43      # Get all players and map...
...
59    def post(self, request, *args, **kwargs):
60      # Handle user deletion...

Source: github.com/jkoppel/django-battleships/pull/1

Remove indirection

Eliminate unnecessary wrapper functions that add complexity without value

pages/_app.tsx

-4 linesRemove Indirection

BEFORE

Unnecessary wrapper function

42  <Layout>
43    <Component {...pageProps} />
44    <UserTracking />
45    <LoginTracking />
46  </Layout>
...
118  function LoginTracking() {
119    return <LoginTracker />;
120  }

AFTER

Direct component usage

42  <Layout>
43    <Component {...pageProps} />
44    <UserTracking />
45    <LoginTracker />
46  </Layout>
...

Simpler & More Direct

Removed 4 lines of unnecessary indirection. The code is now easier to understand and maintain.

Source: github.com/jkoppel/langfuse/pull/2

Separate logic

Extract mixed concerns into focused modules for better testability and reusability

features/auth/hooks.ts → features/auth/storage.ts

-25 lines+3 linesExtract Storage Logic

BEFORE

Storage logic mixed with UI hook

41  const [logins, setLogins] = useState<LastUsedLogin[]>(0);
44  // Load from localStorage on mount
45  useEffect(() => {
47    try {
48      const stored = localStorage.getItem(STORAGE_KEY);
49      if (stored) {
50        const parsed = JSON.parse(stored) as LastUsedLogin[];
51        // Filter out expired entries
52        const now = Date.now();
53        const valid = parsed.filter(
54          (login) =>
55            now - login.timestamp < EXPIRATION_DAYS * 24 * 60 * 60 * 1000,
56        );
57        setLogins(valid);
58      }
59    } catch (error) {
60      console.error("Failed to load last used logins:", error);
61    }
62  }, []);

AFTER

Clean separation

New Module: features/auth/storage.ts

45  export function loadLastUsedLogins(): LastUsedLogin[] {
46    const stored = safeGetJson<LastUsedLogin[]>(
47      localStorage,
48      LAST_USED_STORAGE_KEY,
49    );
51    // Filter expired, update storage...
62    return loaded;
63  }

UI HOOK ONLY

40  export const useLastUsedLogin = () => {
41    const [logins, setLogins] = useState<LastUsedLogin[]>(0);
42    useEffect(() => {
43      const loaded = loadLastUsedLogins();
44      setLogins(loaded);
45    }, []);
...
59    return { logins, setLogins };
60  };

Better Separation of Concerns

Storage logic is now testable independently. The hook is simpler and focused on UI state management.

Source: github.com/jkoppel/langfuse/pull/2

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