With IncrTcl and TclOO, objects must be destroyed manually. If possible, I'd like objects to be cleaned up automatically, for example when a variable holding an object reference goes out of scope at the end of a procedure, or when a variable holding an object reference is set to say "", etc. I also want strong/weak references, to simplify management of objects in certain circumstances.
I've been experimenting with a very simple OO system (owc - objects without classes) to see if I could achieve this, and what I've done so far looks like it works.
Below are three examples, and at the bottom of the page are my sources - a Tcl script that implements owc, and some C code that provides support for strong/weak references.
This example is a variation on http://wiki.tcl.tk/20200 .
proc ::account::account {{ownerName undisclosed}} {
set this [ocreate {deposit withdraw transfer} cleanup {
variables total overdrawLimit owner
}]
oset $this total 0 overdrawLimit 10 owner $ownerName
return $this
}
proc ::account::deposit {amount} {
ocontext total
set total [expr {$total + $amount}]
}
proc ::account::withdraw {amount} {
ocontext total overdrawLimit owner
if {($amount - $total) > $overdrawLimit} {
error "Can't overdraw - total: $total, limit: $overdrawLimit"
}
set total [expr {$total - $amount}]
}
proc ::account::transfer {amount targetAccount} {
ocontext total
withdraw $amount
ocmd $targetAccount deposit $amount
return $total
}
proc ::account::cleanup {} {
ocontext total
if {$total} {
puts "remaining $total will be given to charity"
}
}
# ------------------------------------------------------------------------------
set a [::account::account "John Doe"]
ocmd $a deposit 200
ocmd $a withdraw 15
puts "a = [oget $a total]"
set b [::account::account]
ocmd $a transfer 65 $b
puts "a = [oget $a total], b = [oget $b total]"
puts "Objects: [ocurrent]"
set a ""
puts "Objects: [ocurrent]"
set b ""
puts "Objects: [ocurrent]"
The ocurrent call returns counts of objects by namespace. The output of this script is:
a = 185 a = 120, b = 65 Objects: ::account 2 remaining 120 will be given to charity Objects: ::account 1 remaining 65 will be given to charity Objects:
As can be seen, setting variables that hold object references to "" result in the objects being cleaned.