xcode instance help!

[Istrfly]

Hello, I am new to this forum, but I cannot find any help. I was wondering if anyone knew why the currency converter tutorial comes up with this error when trying to run it.

2004-09-14 20:36:36.054 CurrencyConverter[1158] *** -[ConverterController convertAmount:atRate:]: selector not recognized
2004-09-14 20:36:36.057 CurrencyConverter[1158] *** -[ConverterController convertAmount:atRate:]: selector not recognized

Then nothing happens. I have checked again and again and my code is exactly like the tutorials. However... if I put a + instead of a - in front of the method, it works great. Can anyone please explain this?
Thanks!

 

[SilentPanda]

I'm pulling this from the "I did a few tutorials" memory so it might be wrong but I do know how to code (just not strong in Obj-C).

The - in Obj-C makes the function private to the class whereas the + makes it public to all. Most likely your function is in the wrong class. For example:

Class A has methods:
+myPublicMethod
-myPrivateMethod

Class B could have the following

A = new A;
A.myPublicmethod;

However it could not have:

A.myPrivateMethod;

Unless myPrivateMethod was in class B instead.

That would be my guess as to your problem.

 

[HexMonkey]

The - in Obj-C makes the function private to the class whereas the + makes it public to all.

No, the - represents an instance method and the + represents a static method.

I found a (working) copy of the tutorial that I did when I was learning Objective C, and it turns out that convertAmount:atRate: is a method of the Converter class, but the error you are getting suggests that the message is being sent to the ConverterController class. Check what objects you are sending the convertAmount:atRate: message to.

For reference, I've put a copy of the code from my copy below (hopefully it's the same version).

ConverterController.h:

/* ConverterController */

#import <Cocoa/Cocoa.h>

@interface ConverterController : NSObject
{
    IBOutlet id converter;
    IBOutlet NSTextField *dollarField;
    IBOutlet NSTextField *rateField;
    IBOutlet NSTextField *totalField;
}
- (IBAction)convert:(id)sender;
@end

ConverterController.m:

#import "ConverterController.h"
#import "Converter.h"

@implementation ConverterController

- (void)awakeFromNib {
	[[rateField window] makeKeyAndOrderFront:self];
	[rateField selectText:self];
}

- (IBAction)convert:(id)sender
{
	float rate, amt, total;
	amt = [dollarField floatValue];
	rate = [rateField floatValue];
		
	total = [converter convertAmount:amt atRate:rate];
	
	[totalField setFloatValue:total];
	[rateField selectText:self];
}

@end

Converter.h:

/* Converter */

#import <Cocoa/Cocoa.h>

@interface Converter : NSObject
{
}
- (float)convertAmount:(float)amt atRate:(float)rate;

@end

Converter.m:

#import "Converter.h"

@implementation Converter
- (float)convertAmount:(float)amt atRate:(float)rate {
	return (amt * rate);
} 
@end

 

[bousozoku]

Are you sure that the connections you drew in Interface Builder are correct?

The code could look fine but the hidden information would be pointing to/from the incorrect object in the pane.