how to enable/disable NSToolbarItem

Implement NSToolbarItemValidation Protocol in your window, view or document controller. The documentation gives the following sample code:

-(BOOL)validateToolbarItem:(NSToolbarItem *)toolbarItem {

    BOOL enable = NO;
    if ([[toolbarItem itemIdentifier] isEqual:SaveDocToolbarItemIdentifier]) {

        // We will return YES (enable the save item)
        // only when the document is dirty and needs saving
        enable = [self isDocumentEdited];

    } else if ([[toolbarItem itemIdentifier] isEqual:NSToolbarPrintItemIdentifier]) {

        // always enable print for this window
        enable = YES;
    }
    return enable;
}

You can also use action or tag to determine what toolbar item is being validated. Items are validated frequently, whenever your app is activated or events are dispatched, so they will always be in a valid state.

There is an easier solution :

-(BOOL)validateToolbarItem:(NSToolbarItem *)toolbarItem
{

    return [toolbarItem isEnabled] ;
}

that way you can use [yourToolBarItem setEnabled:YES/NO] ; in your code.

an easy way to do this in swift, or you could port this to objective c is to just set actions

This Disables the item

Mytoolbar.action = nil

This reEnables it

Mytoolbar.action = "Name of a function"

In doing this you would want to replace your IBAction with function so

@IBAction func blehbleh(sender: AnyObject){ Stuff }

would be changed to

func blehbleh(){ Stuff }