Utility for inserting new entries in set X preserving order defined in set M #objective-c #cocoa #collections #sorting #intermediate

add_to_collection_preserving_order.m

/** Utility for inserting new entries in set X preserving order defined in set M */
- (void)_addEntry:(id)entryToInsert toSet:(NSMutableOrderedSet *)mutatingSet respectingOrderIn:(NSMutableOrderedSet *)masterSet
{
    NSInteger entryIdxInMaster = [masterSet indexOfObject:entryToInsert];
    NSAssert(entryIdxInMaster != NSNotFound, @"The setWithOrder must contain the entryToInsert");
    
    // Loop through the set and find the index of the place to insert the new entry
    __block NSInteger idxToInsertBefore = NSNotFound;
    [mutatingSet enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop)
    {
        NSInteger objIdxInMaster = [masterSet indexOfObject:obj];
        if (entryIdxInMaster < objIdxInMaster)
        {
            idxToInsertBefore = idx; // = idx of the obj in the mutating set
            *stop = YES;
        }
    }];
    
    // If not found then the new entry's idx in the masterSet was higher than all the existing ones so append it
    if (idxToInsertBefore == NSNotFound) {
        [mutatingSet addObject:entryToInsert];
    } else {
        [mutatingSet insertObject:entryToInsert atIndex:idxToInsertBefore];
    }
}