Still confused by Objective C variable scope - objective-c

Question

I am trying to get some employee data from a JSON service. I am able to get the data and load it into an NSMutableArray, but I cannot access that array outside the scope of the method that gets the data.
TableViewController h filed
#import <UIKit/UIKit.h>
#import "employee.h"
#interface ViewController : UITableViewController
{
//NSString *test;
//NSMutableArray *employees;
}
#end
And here is my m file:
#define kBgQueue dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
#define scoularDirectoryURL [NSURL URLWithString: #"https://xxxx"]
#import "ViewController.h"
#interface ViewController()
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
dispatch_async(kBgQueue, ^{
NSData* data = [NSData dataWithContentsOfURL:
scoularDirectoryURL];
[self performSelectorOnMainThread:#selector(fetchedData:) withObject:data waitUntilDone:YES];
});
}
- (void)fetchedData:(NSData *)responseData {
NSError* error;
NSMutableArray *jsonArray = [NSJSONSerialization JSONObjectWithData: responseData options: NSJSONReadingMutableContainers error: &error];
id jsonObject = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
NSMutableArray *employees = [[NSMutableArray alloc ]init];
if (!jsonArray) {
} else {
for (jsonObject in jsonArray){
employee *thisEmployee = [employee new];
thisEmployee.fullName = [jsonObject objectForKey:#"$13"];
thisEmployee.state = [jsonObject objectForKey:#"state"];
thisEmployee.city = [jsonObject objectForKey:#"city"];
[employees addObject:thisEmployee];
}
}
}
Any help would be appreciated.
Bryan

Answer 1

You were on the right track. All you have to do is uncomment the NSMutableArray declaration in your #interface, and then change this line:
NSMutableArray *employees = [[NSMutableArray alloc] init];
to this
employees = [[NSMutableArray alloc] init];
Declaring the array in your interface will allow it to be accessed from anywhere within your implementation, or even from other classes and files if you declare it as a public property. When you make a declaration inside a function, that variables scope does not extend to outside of the function.

Answer 2

Just to elaborate a little on the scope of the variables, you have several ways of declaring them. The most used are:
Instance variables, which are declared in your interface and they can be accessed from any method inside the class or inside any method from it's subclasses. For example:
#interface MyObject : NSObject { //this can be any class
NSString *instanceVariable;
}
#implementation MyObject
-(void)someStrangeMethod {
instanceVariable = #"I'm used here";
NSLog(#"%#",instanceVariable);
}
//from subclasses
#interface MySubclassObject: MyObject {
//see that the variable is not declared here;
}
#implementation MySubclassObject
-(void)anotherStrangeMethod {
[super someStrangeMethod]; // this will print the value "I'm used here"
instanceVariable = #"I'm changing my value here"; //here we access the variable;
}
If you want the instance variable to be accessed only from the "owner" class you can declare it after the #private tag. You also have the #protected tag, though that isn't used so much.
If you want to have a variable that can be accessed outside the class, declare it as a property in your interface.
Also you can make the properties private using #private but this will contradict the purpose of the properties.