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TK error - button command within a procedure

Posted by dvorak_user (dvorak_user), 12 January 2008
edit: I sidestepped the issue and got my program to run properly, but I'd still like an answer. Much appreciated!

Hello, all! I'm working on a script with a portion similar to the code below. I can't get it to work quite right, however.

version 1:
Code:
proc something {} {
     set dir "C:\\"
     button .b -text "press me" -command {set temp [tk_getOpenFile -initialdir $dir]}
     pack .b
}
something

result: when button is pressed, I get 'Error: can't read "dir": no such variable'

version 2:
Code:
proc something {} {
     set dir "C:\\"
     button .b -text "press me" -command "set temp [tk_getOpenFile -initialdir $dir]"
     pack .b
}
something

result: prompted to choose a file before button loads.

I really don't know where this script is going wrong, and any help would be appreciated. Thank you!

Posted by admin (Graham Ellis), 13 January 2008
An excellent question.

Curly braces are a deferred block, so the command is stored as you define it and is evaluated later on (and in the root or global context).   But double quoted, the block is evaluated at the time that the proc is run and the component is defined, and in the scope of the proc.

Posted by dvorak_user (dvorak_user), 13 January 2008
Thanks for your explanation - that certainly cleared things up! Much obliged.



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