how to show avg of employees salary in a NSTextField using NSArrayController and cocoa bindings

Question

I am new to cocoa bindings so I tried to make a simple application which will simply calculate avg of employees salary and display it in a text field, using cocoa bindings. I followed these steps:

1. Made the model class : Person with one property for now -

   @property (readwrite, assign) int salary;

2. In the application delegate class I initialized a mutable array : personArray with certain objects like this:

   Person *person1 = [[Person alloc] init];
   person1.salary = 5000;
   
   Person *person2 = [[Person alloc] init];
   person2.salary = 15000;
   
   Person *person3 = [[Person alloc] init];
   person3.salary = 7000;
   
   Person *person4 = [[Person alloc] init];
   person4.salary = 9000;
   
   Person *person5 = [[Person alloc] init];
   person5.salary = 11000;
   
   personArray= [[NSMutableArray alloc] initWithObjects:person1, person2, person3, person4, person5,nil];
   

3. In IB I dropped a NSArrayController object, set its mode as Class - Person, added key salary in attribute pane. Then in bindings pane, binded contents array to ApplicationDelegate class with model key path set to self.personArray.

4. Dropped a NSTextField on window. Binded its value to ArrayController object. Assigned controller key as - arrangedObjects. Assigned Model key path to @avg.salary

When I executed the application I found no value being displayed in the text field.

Can anyone suggest me where I may be wrong or some other best way to accomplish it

Thanks,

Miraaj

Answer 1

The problem reported above is resolved now, I did following improvements to resolve it:

1. I declared property for - personArray in ApplicationDelegate class.

2. In place of assigning Person objects directly to personArray, I first assigned them to a temporary array and then I assigned it to personArray using: -setValue:forKey: method.

It now works as intended :)