[Tutor] passing variables between frames?

[Kent Johnson]

Jeff Peery wrote:
> Hello, I am having trouble with passing variables between frames (Frame1 
> and Dialog1).  I'm using wxpython to write an application. when I run my 
> application the parent frame appears and within the parent frame I can 
> assign values to variables.  I then have a button that launches a child 
> dialog.  I want to access the values from the parent frame in the 
> dialog.  for example say I had a listbox in the parent frame and I 
> choose the first entry 'a' from the list.  I then launch the child 
> dialog and I want to put the value of the selection from the list box 
> into a text field - when I lauch the child dialog a text field appears 
> with the value '0'. From within Frame1 I can use the getselection() 
> function to get the listbox selection. although in the child dialog I 
> tried to use Frame1.listBox.getselection() to get the selection from 
> Frame1. this doesn't work. not sure what to do here? any ideas? thanks.

It's hard to know specifically what is broken without seeing code or error messages. My guess is 
that the variable Frame1 is not in scope in the dialog box code. But I would suggest a different 
approach...

- Make the dialog box code independent of the values of variables in Frame1. Generally for me this 
means packaging up the dialog box in a function or class that is passed the values it needs to use 
and returns some result to the user. A very simple example is a dialog box that presents an error 
message; you could make a function showError(msg) that doesn't know anything about its caller.

- In the event handler for the button in Frame1, gather the values needed by the dialog, launch it, 
get the result and handle it.

This style keeps your dialog code independent of the rest of the program. An immediate benefit is 
that you can write a simple test driver that exercises the dialog without having to create any 
infrastructure. (This is the way I create most dialog boxes. I run it standalone until I am happy 
with its appearance and function, then I integrate it into the rest of the app.) Another long-term 
benefit is the dialogs are reusable; you may not see a need for this but in the long run some of 
them will probably have more than one use.

HTH,
Kent