Question

I’ve got a NSMutableArray (containing NSMutableDictionary instances) bound to an NSArrayController (the NSArrayController is in turn bound to NSTableView columns).

What is the most Cocoa-, and KVO- friendly way of, programmatically :

• adding a new empty object (NSMutableDictionary) to the array?
• removing currently selected object? (after removing, the previous item – if exists – should be selected)

I’ve always been doing this in a way I don’t particularly like – and I’m sure it’s not the best way around (too many lines of code for something so simple : in Cocoa that indicates a wrong take on the subject :-)).

---

My code (quite an overkill, actually) :

---

Adding to the Array

NSMutableArray* oldParams = [paramsArray mutableCopy];

[oldParams addObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:@"Parameter",@"Parameter",@"",@"Value", nil]];
[self setParamsArray:oldParams];

[paramsController setSelectionIndex:[paramsArray count]-1];

Removing currently selected object from the Array

if ([paramsArray count]>0)
{
    int s = [paramsController selectionIndex];

    NSMutableArray* oldParams = [paramsArray mutableCopy];

    [oldParams removeObjectAtIndex:s];

    [self setParamsArray:oldParams];

    if (s<=[paramsArray count]-1)
        [paramsController setSelectionIndex:s];
    else
        [paramsController setSelectionIndex:[paramsArray count]-1];
}

So, what are your opinions on that?

Answer 1

You have to think of your array as the controller’s backing store, and that it’s managing it for you.

Adding an object:

[[self accountsArrayController] addObject:accountDictionary];

Removing the currently selected object:

[[self accountsArrayController] remove:nil];

You’ll have to write another line or two to make that previous item selected, but that’s an exercise I leave to you.