Question

Newbie here. In the following code:

+ (NSString *)descriptionOfProgram:(id)program
{
    NSMutableArray *mutableCopyOfProgram = [program mutableCopy];
    NSString *descr = @"";
    for (int i=0; i<mutableCopyOfProgram.count; i++)
    {
        descr = [descr stringByAppendingString:(@"%@",[mutableCopyOfProgram objectAtIndex:i])];
    }
    return descr;
}

I keep getting an “expression result unused” warning on the code in the loop. But how can that be, when in the next line I return the expression result?

Answer 1

The warning you get is because you should use stringByAppendingFormat: method instead of stringByAppendingString:. Anyway, I would recommend using NSMutableString for building a string. Also, it’s better to use [mutableCopyOfProgram count] instead of mutableCopyOfProgram.count. The following code should work for you:

+ (NSString *)descriptionOfProgram:(id)program
{
    NSMutableArray *mutableCopyOfProgram = [program mutableCopy];
    NSMutableString *descr = [[NSMutableString alloc] init];
    for (int i=0; i < [mutableCopyOfProgram count]; i++)
    {
        [descr appendFormat:@"%@", [mutableCopyOfProgram objectAtIndex:i]];
    }
    return descr;
}