IGListDiff Result Cannot Correctly Transform Original Array to Target Array

[taohailong]

Description:

Using the result of IGListDiff to transform the original array into the target array does not produce the expected output.

Reproduction Steps:

NSArray<NSString*> *oriList = @[@"A", @"B", @"C", @"D", @"E", @"F", @"G", @"H",@"I", @"J", @"K", @"L", @"M", @"N", @"O", @"P",@"Q", @"R", @"S", @"T", @"U", @"V"];
NSArray *newList = @[@"J", @"E", @"C", @"O", @"Q", @"H", @"L", @"G", @"W", @"K"];

IGListIndexSetResult *diff = IGListDiff(oriList, newList, IGListDiffEquality);
NSMutableArray<NSString*> *modifyArray = [oriList mutableCopy];

// 1. Perform deletions
NSArray *deleteModels = [modifyArray objectsAtIndexes:diff.deletes];
[deleteModels enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    NSUInteger removeIndex = [modifyArray indexOfObject:obj];
    NSAssert(removeIndex != NSNotFound, @"Delete element error index %ld, element %@", idx, obj);
    [modifyArray removeObject:obj];
}];

// 2. Perform insertions
[diff.inserts enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL * _Nonnull stop) {
    id insertModel = [newList objectAtIndex:idx];
    NSAssert(insertModel != nil, @"Insert element is nil at index %ld", idx);
    [modifyArray insertObject:insertModel atIndex:idx];
}];

// 3. Perform moves
__auto_type moveArray = [diff.moves sortedArrayUsingComparator:^NSComparisonResult(IGListMoveIndex * _Nonnull obj1, IGListMoveIndex * _Nonnull obj2) {
    return obj1.from > obj2.from ? NSOrderedDescending : NSOrderedAscending;
}];

[moveArray enumerateObjectsUsingBlock:^(IGListMoveIndex * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    id element = oriList[obj.from];
    NSUInteger toIndex = obj.to;
    NSUInteger currentIndex = [modifyArray indexOfObject:element];
    if (currentIndex != toIndex) {
        [modifyArray removeObject:element];
        if (toIndex < modifyArray.count) {
            [modifyArray insertObject:element atIndex:toIndex];
        } else {
            [modifyArray addObject:element];
        }
    }
}];

NSLog(@"Result: %@", modifyArray);

Expected Output:

modifyArray should be:
[@"J", @"E", @"C", @"O", @"Q", @"H", @"L", @"G", @"W", @"K"]


Actual Output:

modifyArray is:
[@"J", @"E", @"C", @"O", @"Q", @"L", @"H", @"G", @"W", @"K"]

[TimOliver]

Hmm, thanks for letting us know @taohailong!

Can you please provide what the actual values inside IGListIndexSetResult *diff are?