Objective-C difference in concatentation methods

Question

Clarification question here. I was originally attempting to concatenate two strings using the stringByAppendingString method:

NSString *dataString = @",";
NSInteger i = 0;
NSString *cycleCountString = @"";
for (i = 0; i<[[self cycleList] count]; i++) {

    cycleCountString = [NSString stringWithFormat:@"cycle#%d,",i];
    [dataString stringByAppendingString:cycleCountString];
}
NSLog(@"DataString is: %@",dataString);

However, the NSLog was just outputing "," as if cycleCountString was not being appended to dataString.

After reading:http://stackoverflow.com/questions/510269/how-do-i-concatenate-strings-in-objective-c , I was able to fix the issue by instead doing a stringWithFromat:

NSString *dataString = @",";
NSInteger i = 0;
NSString *cycleCountString = @"";
for (i = 0; i<[[self cycleList] count]; i++) {

    cycleCountString = [NSString stringWithFormat:@"cycle#%d,",i];
    dataString = [NSString stringWithFormat:@"%@%@",dataString,cycleCountString];


}
NSLog(@"DataString is: %@",dataString);

any idea why the previous method wasn't working? Does stringByAppendingString not work the way I think it does?

thanks!

Answer 1

You're never updating the value of dataString.

dataString = [dataString stringByAppendingString: cycleCountString];