[VEGAN]

Why can't I get a string representation of a number?

I thought [myNumber stringValue] would work but it doesn't. So, what should I do. I've been surfing the web for 2 hours without a solution.

In other words, myNumber = 10 and I wast myString = myNumber = 10 [for a NSTextField and so on].

[Ibson]

If myNumber is an integer, do this:

Code:
NSString *numberAsString = [NSString stringWithFormat:@"%d", myNumber];

If it's a float, replace "%d" with "%f". Type man printf in Terminal to see a full list of tokens.

You say, however, that you want to use myNumber in an NSTextField, in which case you can just use -[NSTextField setIntValue:].

[Ibson]

Originally posted by VEGAN:
I thought [myNumber stringValue] would work but it doesn't.

A fundamental rule of Obj-C programming: you can only send messages to objects. -stringValue is a message, which you're trying to send to a basic C type. Only objects, such as instances of NSNumber are valid receivers of messages.

[VEGAN]

Thanks again! It worked.

I never thought I would have to use stringWithFormat!!!! This is a bit complicated... it might be OK for FLOAT values but for INT? Hmm..

[Ibson]

Originally posted by VEGAN:
This is a bit complicated... it might be OK for FLOAT values but for INT? Hmm..

How so? In a format string:
%@ = Objective-C object (like NSString)
%d = integer
%u = unsigned integer
%f = float
%0.1f = float rounded to 1 decimal place
%g = nicest (IMHO) for floating-point numbers; only displays as many decimal places as necessary
%s = C-string (char *)
%c = C-char
%% = a per cent (%) sign
This is what I remember of the top of my head. It's pretty easy really.

[IamBob]

Code:
{
NSNumber *temp;
int i = 1234;
float f = 0.1234;

temp = [[NSNumber alloc] initWithInt: i ];
// make use of this...
// [temp stringValue]

[temp release];
temp = nil;

temp = [[NSNumber alloc] initWithFloat: f ];
// make use of this...
// [temp stringValue]

[temp release];
temp = nil;
}

Is that easier than using NSString's -stringWithFormat:? I'd go ahead and check the speed of using -stringWithFormat vs. NSNumber. You may find either way acceptable but one will be faster than the other.

// typos fixed

[Ibson]

Originally posted by IamBob:

Is that easier than using NSString's -stringWithFormat:? I'd go ahead and check the speed of using -stringWithFormat vs. NSNumber. You may find either way acceptable but one will be faster than the other.

I did a little test as follows:

Code:
#import <Foundation/Foundation.h>

int main(void)
{
	NSAutoreleasePool *pool;
	int i;
	float time;

	pool = [[NSAutoreleasePool alloc] init];
	time = 0.0;

	for (i = 0; i < 100000; i++)
	{
		NSDate *then = [NSDate date];

		[[NSNumber numberWithInt:1234] stringValue];

		time += [[NSDate date] timeIntervalSinceDate:then];
	}

	NSLog(@"NSNumber Average Time: %f", time / 100000);

	[pool release];

	pool = [[NSAutoreleasePool alloc] init];
	time = 0.0;

	for (i = 0; i < 100000; i++)
	{
		NSDate *then = [NSDate date];

		[NSString stringWithFormat:@"%d", 1234];

		time += [[NSDate date] timeIntervalSinceDate:then];
	}

	NSLog(@"NSString Average Time: %f", time / 100000);

	[pool release];

	return 0;
}

and the results were:

NSNumber Average Time: 0.000021
NSString Average Time: 0.000017

NSNumber Average Time: 0.000022
NSString Average Time: 0.000017

NSNumber Average Time: 0.000022
NSString Average Time: 0.000017

So, as I would have thought, NSString is marginally faster. I imagine that this is because it does need to create and initialize a new object, then send it a message.

[IamBob]

So, as I would have thought, NSString is marginally faster. I imagine that this is because it does need to create and initialize a new object, then send it a message.

After looking at the docs...

NSNumber's stringValue calls another NSNumber method which calls an NSString method and that calls another NSString method and that finally creates your string...

I really thought NSNumber would be faster (b4 I read the docs). I didn't say it was though...I just knew one would be.

I did a few quick tests based off yours to see if I could get better times..

NSNumber flopped (I tried everything I could think of). initWithFormat: is slightly faster then stringWithFormat:. Past that, there's nothing worth mentioning.

Thanks for the tests!