How to return values from gWidgets and handlers?

Question

I am trying to develop a GUI (using gWidgets) for an R package. My plan was to construct a main window holding the data, and with buttons calling small gui wrappers for each fun

Answer 1

A better approach, but one that involves a bigger reworking of your code, is to store GUIs in reference classes.

You call setRefClass with a list of fields (one for each widget), and define an initialise method where the GUI is created. I usually create a function to wrap the call that creates an instance. See setRefClass at the end of the code block.

mainGui <- suppressWarnings(setRefClass( #Warnings about local assignment not relevant 
  "mainGui",
  fields = list(
    #widgets
    w   = "ANY",       #"GWindow"
    txt = "ANY",       #"GEdit"
    btn = "ANY"        #"GButton"
  ),
  methods = list(
    initialize = function(windowPosition = c(0, 0))
    {
      "Creates the GUI"

      w <<- gwindow(
        "Main window", 
        visible = FALSE,
        parent  = windowPosition
      )

      txt <<- gedit(
        "Initial text in main window.", 
        container = w
      )      

      btn <<- gbutton(
        "Send to sub window", 
        container = w
      )      

      addHandlerChanged(
        btn, 
        handler = function(h, ...) {
          subWindow$setText(getText())
        } 
      )

      visible(w) <- TRUE      
    },
    #other methods to access GUI functionality go here
    getText = function() 
    {
      svalue(txt)
    },
    setText = function(newTxt) 
    {
      svalue(txt) <- newTxt
    }
  )
))  

createMainGui <- function(...)
{
  invisible(mainGui$new(...))
}