[kman42]

For some reason I can't get a string to append to another string. Here's the code:

Code:
-(NSCalendarDate *) setTimeLastWUCompleted:(NSString *)time {
    NSString *dateAndTime=@"1972-01-03 ";
    NSLog(@"time=%@",time);
    [dateAndTime stringByAppendingString:time];
    NSLog(@"dateAndTime=%@",dateAndTime);
    [timeLastWUCompleted release];
    timeLastWUCompleted = [[[NSCalendarDate alloc] initWithString:dateAndTime
                               calendarFormat:@"%y-%m-%y %H:%M:%S"] autorelease];
    
        
}

Here's the output:

Code:
2003-05-24 08:01:34.585 F@HMonitor[771] time=14:39:01
2003-05-24 08:01:34.585 F@HMonitor[771] dateAndTime=1972-01-03 
2003-05-24 08:01:34.586 F@HMonitor[771] timeLastWUCompleted=(null)

The NSCalendarDate isn't being set properly because the string doesn't conform to the format because the time isn't being appended to dateAndTime. Any ideas why this isn't working?

thanks,
kman

[entrox]

Despite of me being more of a Lisp guy, I think it's safe to say that the code looks a bit fishy.

First, are you allowed to destructively modify a constant string? Shouldn't you be allocating a fresh NSString object?

Second, is stringByAppendingString supposed to be used destructively? A quick glance at the docs seems to suggest otherwise: from what I gathered it returns a NSString object rather than modifying its receiver.

Try saving the result instead of discarding it: NSString *foo = [dateAndTime stringBy...];

[bousozoku]

Remember that NSString is immutable (cannot be changed) and that NSMutableString is available just for that purpose.

[Gametes]

I haven't tested it, but I think you need to reassign the return to dateAndTime, a la

Code:
dateAndTime = [dateAndTime stringByAppendingString:time];

and for that dateAndTime must be a NSMutableString.

Yet another time when NSString should be NSImmutableString, eh?

[kman42]

Thanks! That was indeed the problem. Interestingly, I didn't have to use NSMutableString. Go figure...

Code:
-(NSCalendarDate *) setTimeLastWUCompleted:(NSString *)time {
    time=[time stringByAppendingString:@" +0000"];
    NSString *dateAndTime=@"1972-01-03 ";
    dateAndTime=[dateAndTime stringByAppendingString:time];
    [timeLastWUCompleted release];
    timeLastWUCompleted = [[NSCalendarDate alloc] initWithString:dateAndTime
                               calendarFormat:@"%Y-%m-%d %H:%M:%S %z"];
    [timeLastWUCompleted setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"PST"]];
    NSLog(@"timedescription=%@",[timeLastWUCompleted description]);
        
}

Output:

Code:
2003-05-24 10:13:27.626 F@HMonitor[1510] timedescription=1972-01-03 08:13:05 -0800

It's always the silly things when your a newbie.

kman

[Chuckit]

Just to clarify, this is the expected behavior.

- (NSString *)stringByAppendingString:(NSString *)aString

Returns a string object made by appending aString to the receiver. This code excerpt, for example:

NSString *errorTag = @"Error: ";
NSString *errorString = @"premature end of file.";
NSString *errorMessage = [errorTag stringByAppendingString:errorString];


produces the string "Error: premature end of file.".

If you want to modify the original string, you'll need to use NSMutableString's -appendString: method.

[Wevah]

You didn't have to use an NSMutableString because it doesn't modify the string object, it returns a new string with another string appended to it—which is also why you had to store the return value in another NSString for it to do anything constructive.

Edit: crap, posted too soon...I didn't read the above post, which explains it as well...