Cannot Get Data from Custom Class - objective-c

Question

I looked around for an answer to this because it seems simple but I could not seem to find something that suffised. I am trying to test a program I have with fake data. I created a StudentData class that possesses a attributes for a student and also has an array to hold them all.
When another class needs them they call a getStudent method (which is the only public part of this class thus far) and sends an ID number to get the name of that student back.
My problem is that I cannot figure out how to parse through the student array to match the student ID numbers with the one that was passed in. Holding the same problem, I cannot figure out how to pull the name out of a student object either.
Here is my code so far:
// StudentData.m
#import "StudentData.h"
#interface StudentData() {
NSString *ID;
NSString *firstName;
}
#property (nonatomic, strong) NSMutableArray *studentArray;
#end
#implementation StudentData
#synthesize studentArray = _studentArray;
- (NSMutableArray *)studentArray {
if(!_studentArray) _studentArray = [[NSMutableArray alloc] init];
return _studentArray;
}
- (void)awakeFromNib {
NSArray *idA = [NSArray arrayWithObjects:#"111", #"685", nil];
NSArray *fnA = [NSArray arrayWithObjects:#"Mark", #"Sam", nil];
for(int i = 0; i < idA.count; i++) {
StudentData *tempCurrentStudent = [[StudentData alloc] init];
ID = [idA objectAtIndex:i];
firstName = [fnA objectAtIndex:i];
[self.studentArray addObject:tempCurrentStudent];
}
}
- (NSString *)getStudentsFirstName:(NSString *)studentID {
NSString *firstName;
for(int i = 0; i < self.studentArray.count; i++) {
if([studentID isEqualToString:[[self.studentArray objectAtIndex:i] self.firstName]]) { // ERROR
fN = [[self.studentArray objectAtIndex:i] self.firstName]; // ERROR
}
}
return firstName;
}
#end
The Error I keep getting is: Expect ']' and the error is pointing to the "self.firstName" lines.
If I use "[self.studentArray objectAtIndex:i].firstName;" I get the error: Property 'firstName' not found on object of type 'id' I even get this error if I make "firstName" a property (both local or public). This makes sense because the array is technically filled with 'id' types. I also know that unlike java I cannot use generics or anything like that.
Any help would be much appreciated and if it needs clarification please let me know! By the way this is for an ipod/ipad app if that helps at all.
Thanks!

Answer 1

Two things :
You're having a name conflict here. You are having a local variable called firstName and the parameter passed to your problem function has the same name.
firstNameis NOT a property unless you define it as one. In this case it's just a normal local variabel. Means that you can't access it using self.firstName but just by firstName. That's one of the reason the coding guidelines say that you should name local variables starting with an underscore ( as you are already doing in the studentArrayproperty). This way you can distinguish if it is a local variable or a property.
Best,
Flo