Objective-C += equivalent?

Question

Sorry for the newbie question, but i cannot find an answer to it.

I have a simple operation. I declare a variable, and then i want to loop through an array of integers and add these to the variable. However, i can't seem to find how to get a += equivalent going in Objective C.

Any help would be awesome.

Code:

NSInteger * result;
for (NSInteger * hour in totalhours)
{
    result += hour; 
}

Answer 1

NSInteger is not a class, it's a typedef for int . You cannot put it into collections like NSArray directly.

You need to wrap your basic data types ( int , char , BOOL , NSInteger (which expands to int )) into NSNumber objects to put them into collections.

NSInteger does work with += , keep in mind that your code uses pointers to them, which is probably not what you want anyway here.

So

NSInteger a = 1, b = 2; 
a += b; 

would work.

If you put them with [NSNumber numberWitInt:a]; etc. into an NSArray , this is not that easy and you need to use -intValue methods to extract their values first.

Answer 2

If totalhours actually contains NSNumber objects you need the following:

NSInteger result = 0;
for(NSNumber* n in totalhours)
{
    result += [n integerValue];
}

Answer 3

The problem is that you are confusing NSInteger (a typedef for int or long ) with a class instance such as NSNumber .

If your totalhours object is an array of NSNumber objects, you'll need to do:

NSInteger result;
for (NSNumber *hour in totalhours)
{
    result += [hour integerValue];
}

Answer 4

No problem using the '+=' operator, just be sure about the objects you are working with... Your code might be:

NSNumber *n; NSUInteger t = 0;
for(n in totalHours) {
    t += [n integerValue];
}
// you got your total in t...

Answer 5

The += operation definitly works. All you need to do is initialize your result variable so it has a start value. Eg NSInteger * result = 0;

Good luck!

Answer 6

Your problem is probably that you're using a pointer to an NSInteger instead of an actual NSInteger. You're also not initializing it. Try this:

NSInteger result = 0;
for (NSInteger * hour in totalhours)
{
    result += *hour; 
}