button -command in for loop (no such variable)

Question

I've got this small loop cycle in TCL

for {set i 1} {$i <= $user} {incr i} {
   grid [ttk::button .seluser.$i -text "$i" -command { set ::user $i }] -column $i -row 1
}

and I'm getting the message

ERROR can't read "i": no such variable

I think it's because -command works like a new proc and that's why it can not identify the variable i.

I don't know how to do it. Can anybody help me?

Andrew Cheong · Accepted Answer · 2012-05-29 14:58:17Z

2

Try quotes instead of braces, so that $i is pre-interpolated. For example,

for {set i 1} {$i <= $user} {incr i} {
    grid [ttk::button .seluser.$i -text "$i" -command " set ::user $i "] -column $i -row 1
}

answered May 29, 2012 at 14:58

Andrew Cheong

30.4k17 gold badges103 silver badges173 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Donal Fellows Over a year ago

It is recommended practice to use list to construct define-time substituted commands, like this: [list set ::user $i]. This is recommended because it is both systematically guaranteed to be correct (Tcl likes to build lists that are also substitution-free commands) and faster to execute (basically, the value can carry a proof with it that no parsing is required).

jk. Over a year ago

It would be good to discuss why quotes work instead of braces

Collectives™ on Stack Overflow

button -command in for loop (no such variable)

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related