Creating Zustand Stores

Creating Zustand Stores for StickerNest

This skill covers creating Zustand stores following StickerNest's established patterns, including TypeScript types, middleware configuration, selectors, and actions.

Store Location

All stores are located in src/state/. Follow the naming convention use{Feature}Store.ts.

Basic Store Template

// src/state/useMyFeatureStore.ts

/**
 * StickerNest v2 - My Feature Store (Zustand)
 * Brief description of what this store manages
 */

import { create } from 'zustand';

// ==================
// Types
// ==================

/** Feature item type */
export interface MyItem {
  id: string;
  name: string;
  value: number;
  createdAt: string;
}

// ==================
// Store State
// ==================

export interface MyFeatureState {
  /** List of items */
  items: MyItem[];
  /** Currently selected item ID */
  selectedId: string | null;
  /** Loading state */
  isLoading: boolean;
  /** Error message if any */
  error: string | null;
}

// ==================
// Store Actions
// ==================

export interface MyFeatureActions {
  /** Add a new item */
  addItem: (item: Omit<MyItem, 'id' | 'createdAt'>) => void;
  /** Remove an item by ID */
  removeItem: (id: string) => void;
  /** Update an existing item */
  updateItem: (id: string, updates: Partial<MyItem>) => void;
  /** Select an item */
  selectItem: (id: string | null) => void;
  /** Set loading state */
  setLoading: (loading: boolean) => void;
  /** Set error state */
  setError: (error: string | null) => void;
  /** Reset store to initial state */
  reset: () => void;
}

// ==================
// Initial State
// ==================

const initialState: MyFeatureState = {
  items: [],
  selectedId: null,
  isLoading: false,
  error: null,
};

// ==================
// Store Creation
// ==================

export const useMyFeatureStore = create<MyFeatureState & MyFeatureActions>()(
  (set, get) => ({
    ...initialState,

    addItem: (item) => {
      const newItem: MyItem = {
        ...item,
        id: crypto.randomUUID(),
        createdAt: new Date().toISOString(),
      };
      set((state) => ({
        items: [...state.items, newItem],
      }));
    },

    removeItem: (id) => {
      set((state) => ({
        items: state.items.filter((item) => item.id !== id),
        selectedId: state.selectedId === id ? null : state.selectedId,
      }));
    },

    updateItem: (id, updates) => {
      set((state) => ({
        items: state.items.map((item) =>
          item.id === id ? { ...item, ...updates } : item
        ),
      }));
    },

    selectItem: (id) => {
      set({ selectedId: id });
    },

    setLoading: (isLoading) => {
      set({ isLoading });
    },

    setError: (error) => {
      set({ error });
    },

    reset: () => {
      set(initialState);
    },
  })
);

// ==================
// Selector Hooks
// ==================

export const useMyItems = () => useMyFeatureStore((state) => state.items);
export const useSelectedItemId = () => useMyFeatureStore((state) => state.selectedId);
export const useSelectedItem = () =>
  useMyFeatureStore((state) =>
    state.items.find((item) => item.id === state.selectedId)
  );
export const useMyFeatureLoading = () => useMyFeatureStore((state) => state.isLoading);
export const useMyFeatureError = () => useMyFeatureStore((state) => state.error);

Store with Persist Middleware

For stores that should persist data to localStorage:

import { create } from 'zustand';
import { persist, createJSONStorage } from 'zustand/middleware';

export const useMyFeatureStore = create<MyFeatureState & MyFeatureActions>()(
  persist(
    (set, get) => ({
      ...initialState,

      // Actions...
    }),
    {
      name: 'my-feature-store', // localStorage key
      storage: createJSONStorage(() => localStorage),

      // Optional: Only persist certain fields
      partialize: (state) => ({
        items: state.items,
        // Don't persist: isLoading, error, selectedId
      }),

      // Optional: Version for migrations
      version: 1,

      // Optional: Migration function
      migrate: (persistedState: any, version: number) => {
        if (version === 0) {
          // Migrate from v0 to v1
          return {
            ...persistedState,
            // Add new fields or transform data
          };
        }
        return persistedState;
      },
    }
  )
);

Store with Devtools Middleware

For debugging with Redux DevTools:

import { create } from 'zustand';
import { devtools } from 'zustand/middleware';

export const useMyFeatureStore = create<MyFeatureState & MyFeatureActions>()(
  devtools(
    (set, get) => ({
      ...initialState,

      addItem: (item) => {
        set(
          (state) => ({
            items: [...state.items, { ...item, id: crypto.randomUUID() }],
          }),
          false, // replace: false (merge)
          'addItem' // Action name for devtools
        );
      },

      // Other actions...
    }),
    {
      name: 'MyFeatureStore', // Store name in devtools
      enabled: process.env.NODE_ENV === 'development',
    }
  )
);

Combined Persist + Devtools

import { create } from 'zustand';
import { persist, devtools, createJSONStorage } from 'zustand/middleware';

export const useMyFeatureStore = create<MyFeatureState & MyFeatureActions>()(
  devtools(
    persist(
      (set, get) => ({
        ...initialState,
        // Actions...
      }),
      {
        name: 'my-feature-store',
        storage: createJSONStorage(() => localStorage),
      }
    ),
    {
      name: 'MyFeatureStore',
      enabled: process.env.NODE_ENV === 'development',
    }
  )
);

Common Patterns

Map-based State (for entities)

export interface EntityState {
  entities: Map<string, Entity>;
}

export interface EntityActions {
  addEntity: (entity: Entity) => void;
  removeEntity: (id: string) => void;
  getEntity: (id: string) => Entity | undefined;
}

export const useEntityStore = create<EntityState & EntityActions>()(
  (set, get) => ({
    entities: new Map(),

    addEntity: (entity) => {
      set((state) => ({
        entities: new Map(state.entities).set(entity.id, entity),
      }));
    },

    removeEntity: (id) => {
      set((state) => {
        const newEntities = new Map(state.entities);
        newEntities.delete(id);
        return { entities: newEntities };
      });
    },

    getEntity: (id) => {
      return get().entities.get(id);
    },
  })
);

Nested State Updates

export interface NestedState {
  settings: {
    appearance: {
      theme: 'light' | 'dark';
      fontSize: number;
    };
    behavior: {
      autoSave: boolean;
      notifications: boolean;
    };
  };
}

export interface NestedActions {
  setTheme: (theme: 'light' | 'dark') => void;
  setFontSize: (size: number) => void;
  toggleAutoSave: () => void;
}

export const useSettingsStore = create<NestedState & NestedActions>()(
  (set, get) => ({
    settings: {
      appearance: { theme: 'dark', fontSize: 14 },
      behavior: { autoSave: true, notifications: true },
    },

    setTheme: (theme) => {
      set((state) => ({
        settings: {
          ...state.settings,
          appearance: {
            ...state.settings.appearance,
            theme,
          },
        },
      }));
    },

    setFontSize: (fontSize) => {
      set((state) => ({
        settings: {
          ...state.settings,
          appearance: {
            ...state.settings.appearance,
            fontSize,
          },
        },
      }));
    },

    toggleAutoSave: () => {
      set((state) => ({
        settings: {
          ...state.settings,
          behavior: {
            ...state.settings.behavior,
            autoSave: !state.settings.behavior.autoSave,
          },
        },
      }));
    },
  })
);

Async Actions

export interface AsyncState {
  data: DataType | null;
  isLoading: boolean;
  error: string | null;
}

export interface AsyncActions {
  fetchData: () => Promise<void>;
  saveData: (data: DataType) => Promise<void>;
}

export const useAsyncStore = create<AsyncState & AsyncActions>()(
  (set, get) => ({
    data: null,
    isLoading: false,
    error: null,

    fetchData: async () => {
      set({ isLoading: true, error: null });
      try {
        const response = await fetch('/api/data');
        const data = await response.json();
        set({ data, isLoading: false });
      } catch (err) {
        set({
          error: err instanceof Error ? err.message : 'Unknown error',
          isLoading: false,
        });
      }
    },

    saveData: async (data) => {
      set({ isLoading: true, error: null });
      try {
        await fetch('/api/data', {
          method: 'POST',
          body: JSON.stringify(data),
        });
        set({ data, isLoading: false });
      } catch (err) {
        set({
          error: err instanceof Error ? err.message : 'Unknown error',
          isLoading: false,
        });
      }
    },
  })
);

Computed Values (Derived State)

export interface ComputedState {
  items: Item[];
  filter: string;
}

export interface ComputedActions {
  setFilter: (filter: string) => void;
  addItem: (item: Item) => void;
}

// Selectors for computed values
export const useFilteredItems = () =>
  useComputedStore((state) => {
    const { items, filter } = state;
    if (!filter) return items;
    return items.filter((item) =>
      item.name.toLowerCase().includes(filter.toLowerCase())
    );
  });

export const useItemCount = () =>
  useComputedStore((state) => state.items.length);

export const useHasItems = () =>
  useComputedStore((state) => state.items.length > 0);

Subscribing to Store Changes

// Subscribe to all changes
const unsubscribe = useMyFeatureStore.subscribe((state) => {
  console.log('State changed:', state);
});

// Subscribe to specific slice
const unsubscribe = useMyFeatureStore.subscribe(
  (state) => state.selectedId,
  (selectedId) => {
    console.log('Selected ID changed:', selectedId);
  }
);

// Don't forget to unsubscribe
unsubscribe();

Testing Stores

// src/state/useMyFeatureStore.test.ts
import { describe, it, expect, beforeEach } from 'vitest';
import { useMyFeatureStore } from './useMyFeatureStore';

describe('useMyFeatureStore', () => {
  beforeEach(() => {
    // Reset store before each test
    useMyFeatureStore.getState().reset();
  });

  it('should add item', () => {
    const { addItem } = useMyFeatureStore.getState();

    addItem({ name: 'Test', value: 42 });

    const { items } = useMyFeatureStore.getState();
    expect(items).toHaveLength(1);
    expect(items[0].name).toBe('Test');
    expect(items[0].value).toBe(42);
    expect(items[0].id).toBeDefined();
  });

  it('should remove item', () => {
    const { addItem, removeItem } = useMyFeatureStore.getState();

    addItem({ name: 'Test', value: 42 });
    const { items: itemsAfterAdd } = useMyFeatureStore.getState();
    const itemId = itemsAfterAdd[0].id;

    removeItem(itemId);

    const { items } = useMyFeatureStore.getState();
    expect(items).toHaveLength(0);
  });

  it('should update item', () => {
    const { addItem, updateItem } = useMyFeatureStore.getState();

    addItem({ name: 'Test', value: 42 });
    const { items: itemsAfterAdd } = useMyFeatureStore.getState();
    const itemId = itemsAfterAdd[0].id;

    updateItem(itemId, { value: 100 });

    const { items } = useMyFeatureStore.getState();
    expect(items[0].value).toBe(100);
    expect(items[0].name).toBe('Test'); // Unchanged
  });

  it('should select item', () => {
    const { addItem, selectItem } = useMyFeatureStore.getState();

    addItem({ name: 'Test', value: 42 });
    const { items } = useMyFeatureStore.getState();

    selectItem(items[0].id);

    const { selectedId } = useMyFeatureStore.getState();
    expect(selectedId).toBe(items[0].id);
  });
});

Existing Stores Reference

Best Practices

1. Keep stores focused - One store per feature/domain
2. Use TypeScript - Define interfaces for state and actions
3. Separate state and actions - Makes types clearer
4. Create selector hooks - For common access patterns
5. Use persist sparingly - Only for data that must survive refresh
6. Include a reset action - For testing and cleanup
7. Use devtools in development - For debugging
8. Avoid storing derived data - Compute in selectors instead