iOS開発-文字列内の複数の同じ文字の位置indexを取得

需要:1つの文字列AStingに複数のabc文字列が存在する可能性があり、すべてのabc文字列をハイライト表示します.
解決策:AStingを巡ってabcが存在するすべての場所のindexを見つけ、indexで文字列を置き換えます.
関連コード:

#pragma mark -        ASting    abc    index
- (NSMutableArray *)getRangeStr:(NSString *)text findText:(NSString *)findText
{
    
    NSMutableArray *arrayRanges = [NSMutableArray arrayWithCapacity:3];
    
    if (findText == nil && [findText isEqualToString:@""])
    {
        
        return nil;
        
    }
    
    NSRange rang = [text rangeOfString:findText]; //        range
    
    if (rang.location != NSNotFound && rang.length != 0)
    {
        
        [arrayRanges addObject:[NSNumber numberWithInteger:rang.location]];//           
        
        NSRange rang1 = {0,0};
        
        NSInteger location = 0;
        
        NSInteger length = 0;
        
        for (int i = 0;; i++)
        {
            
            if (0 == i)
            {
                
               //    abc   
                location = rang.location + rang.length;
                
                length = text.length - rang.location - rang.length;
                
                rang1 = NSMakeRange(location, length);
                
            }
            else
            {
                
                location = rang1.location + rang1.length;
                
                length = text.length - rang1.location - rang1.length;
                
                rang1 = NSMakeRange(location, length);
                
            }
            
            //   range            range
            
            rang1 = [text rangeOfString:findText options:NSCaseInsensitiveSearch range:rang1];
            
            if (rang1.location == NSNotFound && rang1.length == 0)
            {
                
                break;
                
            }
            else//       location   
            
            [arrayRanges addObject:[NSNumber numberWithInteger:rang1.location]];
            
        }
        
        return arrayRanges;
        
    }
    
    return nil;
    
}