What am I doing wrong here? (really noobish problem))

[CSaks]

Hi, I've been attempting to learn Objective-C for around a month now and at the moment I am trying to make a simple vacaction money spending program.

I am trying to implement NSNumber & NSMutableArray into the program and I have run across an error when i go to build and run:

NSNumber *europeDollarTransaction = [[NSNumber alloc] initWithDouble:100.00];
	NSNumber *europeDollarTransaction2 = [[NSNumber alloc] initWithDouble:200.00];
	
	NSMutableArray *europeTransactions = [[NSMutableArray alloc] initWithCapacity:1];
	[europeTransactions addObject:europeDollarTransaction];
	[europeTransactions addObject:europeDollarTransaction2];
	
	
	Budget *europeBudget = [Budget new];
	[europeBudget createBudget: 1000.0 withExchangeRate: 1.2500];
	for (NSNumber *aTransaction in europeTransactions) {
		[europeBudget spendDollars: [aTransaction doubleValue]];
	}
	[europeBudget chargeForeignCurrency:numberEuros];

The error states "Incompatible type for argument 1 of spendDollars" after this line of code

 [europeBudget spendDollars: [aTransaction doubleValue]];

Can someone explain what i've done wrong? Ill admit this is a really noobish question so sorry!

Also I have checked to see if I have misspelled anything/missed out simicolon..etc. but can't see anything

Thanks

[dapis]

Originally Posted by CSaks

Hi, I've been attempting to learn Objective-C for around a month now and at the moment I am trying to make a simple vacaction money spending program.

I am trying to implement NSNumber & NSMutableArray into the program and I have run across an error when i go to build and run:

NSNumber *europeDollarTransaction = [[NSNumber alloc] initWithDouble:100.00];
	NSNumber *europeDollarTransaction2 = [[NSNumber alloc] initWithDouble:200.00];
	
	NSMutableArray *europeTransactions = [[NSMutableArray alloc] initWithCapacity:1];
	[europeTransactions addObject:europeDollarTransaction];
	[europeTransactions addObject:europeDollarTransaction2];
	
	
	Budget *europeBudget = [Budget new];
	[europeBudget createBudget: 1000.0 withExchangeRate: 1.2500];
	for (NSNumber *aTransaction in europeTransactions) {
		[europeBudget spendDollars: [aTransaction doubleValue]];
	}
	[europeBudget chargeForeignCurrency:numberEuros];

The error states "Incompatible type for argument 1 of spendDollars" after this line of code

 [europeBudget spendDollars: [aTransaction doubleValue]];

Can someone explain what i've done wrong? Ill admit this is a really noobish question so sorry!

Also I have checked to see if I have misspelled anything/missed out simicolon..etc. but can't see anything

Thanks

How is the method spendDollars declared?
Does it take a double value?
The error message would suggest that it's not declared to take a double as a parameter.

[CSaks]

Originally Posted by dapis

How is the method spendDollars declared?
Does it take a double value?
The error message would suggest that it's not declared to take a double as a parameter.

Hi, here is my interface;

@interface Budget : NSObject{
	
	float exchangeRate;
	double budget;
	double exchangeTransaction;
}

- (void) createBudget:(double)aBudget withExchangeRate:(float)anExchangeRate;
- (void) spendDollars:(NSNumber*)dollars;
- (void) chargeForeignCurrency:(double)foreignCurrency;

@end

And implementation for spendDollars;

- (void) spendDollars:(NSNumber*)dollars {
	budget -= [dollars doubleValue];
	NSLog(@"Coverting %.2f dollars into foreign currency leaves $%.2f", [dollars doubleValue], budget);
}

And yes I think you might be right, what do you suggest?

Thanks for helping.

[RickSDK]

NSMutableArray's are really meant to hold strings and not numbers, so you might have better luck if you store the numbers as strings and then convert them back to numbers when you use them.

also you are declaring the array as initWithCapacity:1, but then adding 2 values. not sure but you might be better off setting the capacity higher or leaving it off all-together. try this:

NSMutableArray *europeTransactions = [[NSMutableArray alloc] init];

[europeTransactions addObject:[NSString stringWithFormat:@"%d", europeDollarTransaction]];

[RickSDK]

I think i see the problem:

you function is looking for NSNumber:

- (void) spendDollarsNSNumber*)dollars

but you are trying to pass in a doubleValue

try using float for everything to keep things consistent (and be sure to leave off the asterisk!):

- (void) spendDollars:(float)dollars {

[europeBudget spendDollars: [aTransaction floatValue]];

[CSaks]

Hi guys, thanks for all the help, after hours I have finally managed to work out what the problem was.

If you are interested; In the implementation I had already specified that it was a doubleValue:

- (void) spendDollars:(NSNumber*)dollars {
	budget -= [dollars doubleValue];
	NSLog(@"Coverting %.2f dollars into foreign currency leaves $%.2f", [dollars doubleValue], budget);
}

So in this line of code I didn't need to specify that it was doubleValue:

[europeBudget spendDollars: [aTransaction doubleValue]];

So instead I just put:

[europeBudget spendDollars: aTransaction];

Thanks for all the help! Im sure I'll be back again soon enough needing more with another problem

[baja_yu]

Originally Posted by RickSDK

NSMutableArray's are really meant to hold strings and not numbers, so you might have better luck if you store the numbers as strings and then convert them back to numbers when you use them.

That's wrong on multiple levels. NSArrays are meant to hold objects of any kind. They don't care what objects and they don't have to be the same kind. Holding numbers as strings is also a bad idea. In many cases you can lose precision and in most cases you will use more memory and processing power by converting from one to the other all the time.

[michal26]

I think you are passing through doubleValue you should try using float and it might solve your problem.