How to send values to Ivar in method - objective-c

Question

new to Objective-C and keeping it very very simple I'm looking to understand one thing at a time... I set up a very simple class called student all it does is add two numbers trying to see how things pass into and back from methods) **I rewrote the code ==>> look at end to see the version that works **
If I have a method that has
#property (nonatomic) int firstNum;
#property (nonatomic) int secondNum;
and I have an instance of my class called student I assign a value to firstNum like student.firstNum = 100; student.secondNum = 77; that is easy and the method adds them and sends the sum in a return
But in main I tried assigning it from an array and it did not work I tried
student.firstNum = [myIntegers objectAtIndex:0];
and
student.firstNum = [myIntegers objectAtIndex:i]; //using a for loop with i index
it says incompatible pointer to integer conversion
Here is the snippet from main I tried it's not complete it just is trying to set firstNum eventually I will also set up secondNum and send each pair to the method to get added together but for now I am stuck trying to get the firstNum assigned the value in myIntegers[i] to start
NSMutableArray *myIntegers = [NSMutableArray array];
for (NSInteger i= 0; i <= 10; i++) {
[myIntegers addObject:[NSNumber numberWithInteger:i]]; // this works up to here
student.firstNum = [myIntegers objectAtIndex:i]; // this does not work
}
I also tried [i].
Here is my method:
- (int)addNumbers {
int sum = self.firstNum + self.secondNum;
return sum;
}
HERE IS WHAT WORKS : assuming I have a student object
.m
(long)addNumbers:(NSNumber *)x :(NSNumber *)y {
long sum;
sum = [x integerValue] + [y integerValue];
return sum;
}
main
NSMutableArray *myIntegers1 = [NSMutableArray array];
NSMutableArray *myIntegers2 = [NSMutableArray array];
for (NSInteger i= 0; i <40; i++) {
[myIntegers1 addObject:[NSNumber numberWithInteger:i]];
[myIntegers2 addObject:[NSNumber numberWithInteger:i]];
long sum = [student addNumbers:[myIntegers1 objectAtIndex:i] :[myIntegers2 objectAtIndex:i]];
NSLog(#" The sum is %ld", sum);
}

Answer 1

You are creating a properties of type int, but in your for loop, you are trying to assign them an NSNumber.
NSNumber is a simple container for a c data item and can hold int, float, char, bool, etc.
Change your loop to be like that:
for (NSInteger i= 0; i <= 10; i++) {
[myIntegers addObject:[NSNumber numberWithInteger:i]];
student.firstNum = [[myIntegers objectAtIndex:i] intValue]; // this 'extracts' the int value from the NSNumber
}