🐛 [Bug] Duplicate Conversion Constants — `converter_screen.dart` Bypasses `AppConstants`

[Dr-Usman]

🐛 Bug: Duplicate Conversion Constants — converter_screen.dart Ignores AppConstants

📋 Description

The app has a dedicated constants class AppConstants in lib/constants/app_constants.dart designed as the single source of truth for gold unit conversion factors. However, lib/converter_screen.dart re-declares the exact same constants locally and never imports AppConstants — completely bypassing it.

This means there are two separate definitions of the same values in the codebase. If a conversion factor ever needs to be updated (e.g., correcting precision), a developer must update it in both files — and forgetting one will introduce a silent calculation discrepancy with no compile-time error.

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🔍 Evidence

lib/constants/app_constants.dart (the intended source of truth):

class AppConstants {
  static const double tolaToGram  = 11.66;
  static const double mashaToGram = 0.972;
  static const double anaToGram   = 0.72875;
  static const double rattiToGram = 0.1215;
}

lib/converter_screen.dart (duplicate — lines 32–35):

static const double tolaToGram  = 11.66;
static const double mashaToGram = 0.972;
static const double anaToGram   = 0.72875;
static const double rattiToGram = 0.1215;

converter_screen.dart does not import app_constants.dart and uses its own local copies.

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❌ Current Risk

• Any future change to a conversion factor in AppConstants will have zero effect on actual calculations, since converter_screen.dart uses its own copies
• This is a silent bug risk — calculations appear correct but the wrong values could be used without warning
• Violates the DRY (Don't Repeat Yourself) principle and makes maintenance error-prone

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✅ Expected Behavior

converter_screen.dart should import and reference AppConstants directly, with no local duplicate declarations.

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🔧 Fix Required

Step 1 — Add import to lib/converter_screen.dart:

import 'package:gold_weight_converter/constants/app_constants.dart';

Step 2 — Remove the 4 local constant declarations from converter_screen.dart (lines 32–35):

// DELETE these lines:
static const double tolaToGram  = 11.66;
static const double mashaToGram = 0.972;
static const double anaToGram   = 0.72875;
static const double rattiToGram = 0.1215;

Step 3 — Update all usages in converter_screen.dart to use AppConstants:

// Before:
totalGrams += tola * tolaToGram;

// After:
totalGrams += tola * AppConstants.tolaToGram;

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🏷️ Priority

🔴 High — This is a latent maintenance bug that will silently cause calculation errors if constants ever diverge between the two files.

📎 Flutter Files to Modify

File	Action
lib/converter_screen.dart	Remove duplicate constants, add AppConstants import, update all references
lib/constants/app_constants.dart	No changes needed — this is already correct