void value error

[MuffinMan]

This is the series sum of 1/2i code

Code: (Objective-C)

#import <Foundation/Foundation.h>


@interface Fraction2 : NSObject {
	
	int numerator;
	int denominator;
	
}

@property int numerator, denominator;

-(void)print;
-(double)convertToNum;
-(void) setTo:(int)n over:(int)d;
-(void)reduce;
-(void)add: (Fraction2 *)f;


@end

Code: (Objective-C)

#import "Fraction2.h"


@implementation Fraction2

@synthesize numerator, denominator;

-(void)print {
	NSLog(@"%i/%i",numerator,denominator);
}


-(void) setTo:(int)n over:(int)d {
	numerator=n;
	denominator=d;
}

-(double)convertToNum {
	
	if (denominator!=0) {
		return(double) numerator/denominator;
	} else { return 1.0;} 
	
}



-(void)reduce {
	
	int u,v, temp;
	
	u = numerator;
	v= denominator;
	
	while (v!=0) {
		temp = u%v;
		
		u = v;
		
		v = temp;
	}
	
	numerator /= u;
	
	denominator /=u;
}





-(void)add: (Fraction2 *)f {
	
	// a/b + c/d =  (a*d + b*c)/ b*d
	
	numerator = numerator* f.denominator + denominator * f.numerator;
	
	denominator = denominator * f.denominator;
	
	[self reduce];
	[self print];
	
}
@end

Code: (Objective-C)

#import "Fraction2.h"

int main (int argc, char *argv[])
{
	NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	Fraction2 *aFraction = [[Fraction2 alloc]init];
	
	
	
	Fraction2 *sum =[[Fraction2 alloc]init], *sum2;
	
	int n,i,pow2;
	
	[sum setTo:0 over:1]; 
	
	
	scanf("%i",&n);
	
	pow2= 2;
	
	for(i=1;i<=n;++i){
		
		[aFraction setTo:1 over:pow2];
		
		sum2 = [sum add: aFraction];
		[sum release];
		
		sum = sum2;
		
		pow2 *= 2;
		
	}
	
	
	NSLog(@"The sum is %f:",sum);
	
	
	
	
	
	sum.release;
	sum2.release;
	
	
	
	
	
	aFraction.release;
	
	
	
	[pool drain];
	return 0;
}

I am getting the "void value not ignored as it ought to be" error only at the line "sum2 = [sum add: aFraction];" in the program section, what I am doing wronag?

[MuffinMan]

and oh, don't mind the  [self print]; in the definition, I used this for a normal fraction before, i know i should remove it here....

[seerex]

not sure if this fixes it, but you are trying to print the sum using the float print:

Code: (Objective-C)

NSLog (@"%f", sum);

You cant write it, since sum is a variable that holds a reference to an object.

[dharr19]

Hi,

I noticed that the return type of the add method was void

Code: (Objective-C)

-(void)add: (Fraction2 *)f {  

but here you are expecting add to return a value to sum2

Code: (Objective-C)

sum2 = [sum add: aFraction];

Hope this helps
David

[skochan]

FYI, while it's syntactically correct to write a statement such as sum.release, it's not considered good programming style.   The dot operator was really meant to be used with property's; typically to set/get the value of an instance variable.   Other methods that do work (like calculate the sum of two fractions, release an object, etc.) are labeled as "Tasks" in Apple's documentations.  Tasks are typically not executed using the dot operator; the traditional bracketed message expression is the preferred syntax.

Cheers,

Steve

[MuffinMan]

FYI, while it's syntactically correct to write a statement such as sum.release, it's not considered good programming style.   The dot operator was really meant to be used with property's; typically to set/get the value of an instance variable.   Other methods that do work (like calculate the sum of two fractions, release an object, etc.) are labeled as "Tasks" in Apple's documentations.  Tasks are typically not executed using the dot operator; the traditional bracketed message expression is the preferred syntax.

Cheers,

Steve

Noted.

Thank you.

[MuffinMan]

I solved the problem and the outputs are correct,

My main mistake that I've put  #import Fraction2.h instead of #import Fraction3.h  ooops.


my other big mistake was the -(void) add: ,   I didn't see it because I thought I copied from the 7.5 code I made earlier, but it seems that I made my Fraction3 (7.6) over  a more earlier Fraction program where the method of add: was void.


I also corrected the other couple things mentioned by users here.   Thank you everyone.


Btw, that made me think of another question:

How can I properly duplicate a xCode  project?   I couldn't find a proper way to do it other than copying/pasting the codes one by one .....

[fujilla]

You could duplicate the project in the finder, however you will not be able to change the name of the copied project.

The best way that I know of is to create a new project, then drag and drop (from Xcode) the classes you want from the original project into the new project, and select the "Copy" radio button in the window that appears.

Nick
http://myfirstiphoneapp.co.uk