Step #3: Replacing the Item

Now that we have the app bar item, we can get control when it is clicked and update our repository with a revised ToDoModel.

Create this save() function on EditFragment:

  private fun save() {
    binding?.apply {
      val model = motor.getModel()
      val edited = model?.copy(
        description = desc.text.toString(),
        isCompleted = isCompleted.isChecked,
        notes = notes.text.toString()
      ) ?: ToDoModel(
        description = desc.text.toString(),
        isCompleted = isCompleted.isChecked,
        notes = notes.text.toString()
      )

      edited.let { motor.save(it) }
    }
  }

Here we:

• Retrieve our current ToDoModel from the viewmodel
• Use the copy() function on our data class to create a revised instance of ToDoModel with the data from the form
• If, inexplicably, getModel() returned null, create a new ToDoModel with the data from the form
• Tell the SingleModelMotor to replace the existing ToDoModel for this ID with this new or revised model

Then, arrange to call this save() method when the user clicks on the “save” app bar item, by adding this onOptionsItemSelected() function to EditFragment:

  override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
      R.id.save -> {
        save()
        return true
      }
    }

    return super.onOptionsItemSelected(item)
  }

If you run the app, select some to-do item, make some change to that item, then click that app bar item… nothing seems to happen. But, if you then press BACK to return to the DisplayFragment, then BACK again to return to the list, you will see that… the list appears to be unchanged.

These are problems. And, we will fix them in the next couple of steps.