Array Controller not updating Table View until "Add" button is pressed

Question

I'm new to Cocoa and Objective-C, so I'm following the Lynda courses and learning a lot. Thing is, I've encountered a problem that I cannot figure out, even though I seem to be doing it exactly the same way...

Basically, I'm trying to get a Table View hooked up through bindings to an Array Controller, just to list out the contents of a simple NSMutableArray in my code. I'd gotten it all hooked up properly, but no matter what I did it wasn't displaying anything when I ran the program.

Here's where it gets weird: on a lark, I added a "+" button and hooked it into the "add" function of the Array Controller, and when I ran the app and clicked that button, it not only added a new line, but it displayed the whole array as well! Apparently everything had been hooked up properly the whole time, it just wasn't displaying the information. Further experimentation revealed that I could make any changes I wanted to the array, whether in the original code or during the runtime of the app, but they would only be updated in the Table View when I clicked that "+" button.

I feel like this is probably a simple solution, just some "Continuous" box that needs to be checked or something, but I cannot for the life of me find it... Can anyone point out what I need to do to get my TableView to show its contents automatically?

(Also, I don't know if this is related or not, but none of the "Model Key Path" fields in the inspector are offering suggestions as I type, which they do in the Lynda course. The app works fine if I manually type everything in, but it says "no completions found" the whole time.)

Thank you in advance for helping out a n00b!

Answer 1

none of the "Model Key Path" fields in the inspector are offering suggestions as I type

As I understand it this is probably because the NSMutableArray that holds your data array i.e. dogPound or similar, isn't also declared as a property, only an instance variable.
Declare the property @property NSMutableArray * dogPound; and change the instance variable declaration to _dogPound and I think interface builder should offer you the auto-completes.

Answer 2

I'm new to Cocoa and Objective-C

Me too.

I'd gotten it all hooked up properly,

In about 30 minutes, I can get everything setup with a custom class like Dog, and another class called AppController that consists of one instance variable: NSMutableArray* dogPound. The init() method for the AppController class creates the array and adds some Dog instances to the array. I also bound an NSArrayController to the dogPound array, and I bound the NSTableView columns to the NSArrayController. After I Build&Run the NSTableView displays the information for each Dog instance in the dogPound array.

I also tried a simpler version where there is no Dog class and the array in the AppController class just consists of some NSString objects. Once again, I was able to successfully bind an NSArrayController to the array and bind the table's columns to the NSArrayController, so that an NSTableView displayed all the NSString's in the array.

You need to post your exact code, and you need to write down every step you did in IB, which of course is a huge pain in the ass, but it's the only way anyone will be able to help you.

Here's where it gets weird: on a lark, I added a "+" button and hooked it into the "add" function of the Array Controller, and when I ran the app and clicked that button, it not only added a new line, but it displayed the whole array as well!

Of course. The add: method in the NSArrayController adds a new item to the array and then signals the NSTableView that it should reload the data, i.e display everything that's currently in the array.

I feel like this is probably a simple solution, just some "Continuous" box that needs to be checked or something,

Nope, nothing like that.

none of the "Model Key Path" fields in the inspector are offering suggestions as I type

Lack of autocompletion choices is a big hint that you are doing something wrong--even though I find I can't always figure it out, so I just keep typing. Did you remember to start your bindings in the Attributes Inspector(Object Controller section) for the NSArrayController? In IB, did you create an instance of your AppController class, or whatever you called the class that contains the NSMutableArray, by dragging an Object onto MainWindow.xib?