example array
   TimeRunning = @[@"01:10:50", @"01:03:23", @"03:04:22"];//arrayStrig

timeRunning = [obj valueForKey:@"oficialTime"];
NSLog(@"%@",timeRunning); //out 01:02:03 10:10:02 10:38:59

float ofcTime =[[obj valueForKey:@"oficialTime"]floatValue];
NSLog(@"float : %f",ofcTime); //out 1.000000 10.000000 10.000000

NSString * dataString = [TimeRunningString stringByReplacingOccurrencesOfString:@":" withString:@"."];
NSLog(@"??????: %@",dataString); //out 01.02.03  10.10.02  10.38.59

NSArray *listItems = [dataString componentsSeparatedByString:@"."];
NSLog(@"Real: %@",listItems);//out  10,
                                    10,
                                    02

NSString *covert = [NSString stringWithFormat:@"%@",listItems];
NSLog(@":%@",covert);   //out  10,
                               10,
                               02

float realArrary = [dataString floatValue];
NSLog(@"floatP : %f",realArrary); out 2.030000 10.000000 10.100000