OOP: Properties Containing Objects

Hi All,

I defined a class called instr (which is short for instrument) that is derived from a handle class. The instr class sets up a remote connection to a specified instrument. I also created two other handle classes: source and state, so that you can interact with the instrument once you are connected to it. These classes are instantiated by the instr class in two separate properties.

I have a question about what to do next. I want to prevent access to the instr.source and instr.state objects unless you have successfully connected to the instrument. I have a property in the instr class that I can query to see whether I am connected or not. But based on http://www.mathworks.com/help/matlab/matlab_oop/properties-containing-objects.html , I am not sure how to prevent someone from doing, say, instr.state.TurnOnOutput, when the instrument isn't even connected. The only way I can think of is for every method in the source and state class to have a check whether you are connected, but this seems tedious.