Fix Store Getter: Return Map Tiles Array

In this article, we'll dive into the process of fixing a crucial part of our application's store: the currentMap getter. The goal is to modify it to return an array of tiles instead of the entire Map object. This is a critical adjustment that ensures our application works efficiently and accurately.

Understanding the Issue

Currently, the currentMap getter in our store is set up to return the entire Map object. This is not ideal because we often only need the array of tiles within the map. By returning the entire object, we're potentially passing around more data than necessary, which can lead to performance bottlenecks and increased memory usage. The fix involves changing the getter to specifically return the tiles array, which contains the essential tile data for rendering and other operations.

The Current Implementation (WRONG)

Let's take a look at the current, incorrect implementation of the currentMap getter:

// src/store/store.js:155
// Current (WRONG):
currentMap: state => state.soldiers.currentWar.map

As you can see, this getter simply returns the map property from the currentWar object within the state. While this provides access to the Map object, it doesn't isolate the tiles array, leading to the issues mentioned earlier.

The Correct Implementation

To fix this, we need to modify the getter to specifically return the tiles array. Here's the corrected implementation:

// Should be:
currentMap: state => {
  if (!state.soldiers.currentWar) return null;
  return state.soldiers.currentWar.map.tiles;
}

This updated getter first checks if state.soldiers.currentWar exists to avoid errors when there is no active war. If it exists, it returns the tiles array from the map object. This ensures that we only retrieve and use the necessary data, improving performance and reducing memory consumption.

Implementing the Fix

To implement this fix, you'll need to modify the src/store/store.js file. Specifically, you'll need to find the currentMap getter (around line 155) and replace it with the corrected implementation provided above. This simple change will have a significant impact on the efficiency of your application.

Testing the Changes

After implementing the fix, it's crucial to ensure that it works as expected and doesn't introduce any regressions. This is where unit tests come in. We'll be adding tests to tests/lib/store.spec.js to verify the behavior of the currentMap getter.

Unit Test Requirements

Our unit tests will cover the following scenarios:

• currentMap getter returns array (not Map object): This test verifies that the getter now returns an array, as intended, and not the entire Map object.
• Returned array is 20 rows × 20 columns: This test ensures that the returned array has the correct dimensions, which is crucial for our map representation.
• Each element is a Tile object: This test verifies that each element in the array is indeed a Tile object, ensuring the integrity of the map data.
• Returns null when no war active: This test checks that the getter returns null when there is no active war, preventing potential errors and ensuring graceful handling of edge cases.

Writing the Unit Tests

To write these tests, you'll need to use a testing framework like Jest or Mocha, along with an assertion library like Chai. Here's a basic outline of how the tests might look:

// tests/lib/store.spec.js

describe('store', () => {
  describe('currentMap getter', () => {
    it('should return an array (not Map object)', () => {
      // Test implementation
    });

    it('should return an array with 20 rows and 20 columns', () => {
      // Test implementation
    });

    it('should return an array where each element is a Tile object', () => {
      // Test implementation
    });

    it('should return null when no war is active', () => {
      // Test implementation
    });
  });
});

Inside each test case, you'll need to set up the store state, call the currentMap getter, and then use assertions to verify the results. For example, to test if the getter returns an array, you might use expect(Array.isArray(currentMap)).toBe(true);.

Detailed Steps for Implementation

To ensure a smooth and successful implementation, let's break down the steps involved:

1. Navigate to src/store/store.js: Open this file in your code editor.

2. Locate the currentMap getter: Scroll through the file or use your editor's search function to find the currentMap getter definition. It should be within the store's getter section.

3. Replace the existing getter with the corrected implementation:

   currentMap: state => {
     if (!state.soldiers.currentWar) return null;
     return state.soldiers.currentWar.map.tiles;
   }
   

4. Save the changes: Make sure to save the file after making the changes.

5. Navigate to tests/lib/store.spec.js: Open this file in your code editor.

6. Add a new describe block for the currentMap getter: If one doesn't already exist, add a new describe block to group the tests for the currentMap getter.

   describe('currentMap getter', () => {
     // Test cases will go here
   });
   

7. Add the unit test cases: Implement the four unit test cases as outlined in the