R Tcl/Tk: OnReset not working after OnSubmit

Question

In the following code I would like to reset the entry fields, but once I hit the Submit button, I can not reset them any more. If I do Reset before the Submit button then everything is ok. What am I missing?

library(tcltk);

doneInput <- tclVar(0)

tkwindow <- tktoplevel();

l.directory <- tklabel (tkwindow, text = "directory path: ");
l.folder1 <- tklabel (tkwindow, text = "folder name: ");
l.folderO <- tklabel (tkwindow, text = "folder name: ");

o.directory <- tclVar("Enter directory path ...");
o.folder1 <- tclVar("Enter folder name ...");
o.folderO <- tclVar("Enter folder name ...");

e.directory <- tkentry (tkwindow, textvariable = o.directory);
e.folder1 <- tkentry (tkwindow, textvariable = o.folder1);
e.folderO <- tkentry (tkwindow, textvariable = o.folderO);

tkgrid (l.directory, e.directory);
tkgrid (l.folder1, e.folder1);
tkgrid (l.folderO, e.folderO);

tkgrid.configure (l.directory, l.folder1, l.folderO, sticky="e");
tkgrid.configure (e.directory, e.folder1, e.folderO, sticky="w");

OnReset <- function()
{
    tclvalue (o.directory) <<- "path ...";
    tclvalue (o.folder1) <<- "name ...";
    tclvalue (o.folderO) <<- "name ...";

    tkconfigure (b.submit, state = "normal");
}
b.reset <- tkbutton (tkwindow, text = "Reset", command = OnReset)

OnSubmit <- function()
{
    o.directory <<- tclvalue (o.directory);
    o.folder1 <<- tclvalue (o.folder1);
    o.folderO <<- tclvalue (o.folderO);

    print (o.directory);
    print (o.folder1);
    print (o.folderO);

    if (nchar (o.directory) > 0 && 
        nchar (o.Folder1) > 0 &&
        nchar (o.FolderO) > 0)
        tclvalue (doneInput) <- 1;
}
b.submit <- tkbutton (tkwindow, text = "Submit", command = OnSubmit);
tkgrid (b.submit, b.reset, sticky="e", padx=10, pady=10);

tkwait.variable (doneInput)

print (paste ("directory: ", o.directory));
print (paste ("folder1: ", o.folder1));
print (paste ("folderO: ", o.folderO));

Why are you using `tkwait.variable`? Also (just as a style comment), you don't need semicolons at the end of R code lines. — Thomas, Jul 29 '14 at 19:15
It is not in the code that I posted but I want these tkentries to be valid before the code continues on. As for the semicolons ... I have 20 years in C/C++. I am used to them. It is almost automatic. — gaitat, Jul 29 '14 at 19:18
sorry, fixed it. Thats what I get for having two version of code. And obviously the if-statement that will change the value of `doneInput` is only there to do some kind of validation and is always true with the given data strings. — gaitat, Jul 29 '14 at 21:51

Thomas · Accepted Answer · 2014-07-29T21:53:38.007

0

The issue here is the <<- operator used inside the functions (e.g., o.directory <<- tclvalue (o.directory);, etc.). Replacing them with <- solves your problem.

Leaving everything else the same, if you change your OnReset and OnSubmit functions to the following, you should get your intended result:

OnReset <- function()
{
    tclvalue (o.directory) <- "path ...";
    tclvalue (o.folder1) <- "name ...";
    tclvalue (o.folderO) <- "name ...";

    tkconfigure (b.submit, state = "normal");
}

OnSubmit <- function()
{
    a <- tclvalue (o.directory);
    b <- tclvalue (o.folder1);
    c <- tclvalue (o.folderO);

    print (a);
    print (b);
    print (c);

    if (nchar (a) > 0 && 
        nchar (b) > 0 &&
        nchar (c) > 0)
        tclvalue (doneInput) <- 1;
}

edited Jul 29 '14 at 21:53

answered Jul 29 '14 at 19:22

Thomas

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thank you but can you briefly explain the difference bettwen ` – gaitat Jul 29 '14 at 19:28
@gaitat There are some answers on the distinction here: http://stackoverflow.com/questions/2628621/how-do-you-use-scoping-assignment-in-r – Thomas Jul 29 '14 at 19:39
sorry but when I use ` – gaitat Jul 29 '14 at 21:18
1

@gaitat Okay, there are actually several issues here. (1) Your `tkwait.variable()` call is waiting a variable that you never change, so you'll never break out of the tcl event loop. (2) You're initializing tcl variables and then later (in `onSubmit`) trying to overwrite them as simple character strings (every time you `< – Thomas Jul 29 '14 at 21:33
Updated the code above to show that I am waiting until the input is validated. So what I would like is `onSubmit` to get the values of the tkentries and continue my processing. But I would also like to be able to `reset` the tkentries to their original values. The code above does not accomplish both these tasks. Just one. – gaitat Jul 29 '14 at 21:42

R Tcl/Tk: OnReset not working after OnSubmit

1 Answers1