iPhone: Problems with Formatted String (Objective C)

Question

I need help. How come this does not work:

NSProcessInfo *process = [NSProcessInfo processInfo];
NSString *processName = [process processName];
int processId = [process processIdentifier];
NSString *processString = [NSString stringWithFormat:@"Process Name: @% Process ID: %f", processName, processId];
NSLog(processString);

But this does:

NSLog(@"Process Name: %@ Process ID: %d", [[NSProcessInfo processInfo] processName], [[NSProcessInfo processInfo] processIdentifier]);

Answer 1

Your format string is bad: processId is an int not a float.

Use -Wformat to get rid of this kind of errors.

Answer 2

Your format contains an error, you've swapped the @ and % for the [NSString stringWithFormat:]. It will work for the log but not for the string creation, because the format is %@ not @%.

Answer 3

• %@: Output the string form of an object (including NSString).
• %f: Output a floating point number (float)
• %d: Output an integral number (int)
• %x: Output hexadecimal form of a number

Your original NSString:stringWithFormat: had two issues:

1. @% should be %@ to output an NSString.
2. You use %f instead of %d to output an int.