[SOLVED] Swift 4: Read Data from Objective-C-Object

Swift 4: Read Data from Objective-C-Object

I have an app in Swift4 with some Objective-C-objects integrated with a Bridging-Header. That works fine sending data to the swift part with notifications. I want to get data from within a swift function in rCNCViewController from its Objective-C-object AVR. That class has an instance variable motorsteps that is initialized to 48 in awakeFromNib and can be used in the whole class.

class in swift:

class rViewController: NSViewController, NSWindowDelegate
{

}

Subclass:

class rCNCViewController:rViewController
{
  ...
   
  var AVR = rAVRview()
  ...

Class in Objectiv-C-part:

@interface rAVRview:NSViewController <NSTableViewDataSource,NSTableViewDelegate>
{
  ...
  IBOutlet   id       xy;
  ...
}
// variables
  ...
  int motorsteps;
  ...

@end

Get-function in AVR:

- (int)motorsteps
{
    return motorsteps;
}

Calling function in swift part:

guard let steps:Int32 = AVR?.motorsteps()  else {return}

The returned value of steps is 0. Observing the function call to AVR in the debugger shows that motorsteps in AVR is 0. The other objects of AVR are all 0x00.

Changing motorsteps() to returning a constant value returns that value correctly.

After the call from the swift part, the value of the variable motorsteps in AVR is unchanged 48. Why are the AVR objects in the call from the swift part not valid?

Solution

awakeFromNib is only called when an object is loaded from a XIB or Storyboard file. You're creating AVR using its init instead:

var AVR = rAVRview()

You should not expect AVR's awakeFromNib to be called in this case. If you're using a Storyboard (or standalone XIB), then you would define this as an @IBOutlet and connect it in the Storyboard editor. If you're manually creating these views, then you will need to initialize them in initWithFrame: (or potentially init:), not in awakeFromNib.