Sarnold thinks that classes should look - as possible as they can - like namespaces, because it is the current encapsulation model. It may be extreme, but some developers may want to convert quickly a namespace in a Class or Megawidget - while the opposite cannot be as simple. I would like to see:
namespace class foo {
common counter
variable names
proc __init__ {args} {
common counter
incr counter
variable names
array set names $args
}
# it has to look like a normal Tcl proc, so it has an arglist
proc __destroy__ {} {
common counter
incr counter -1
}
proc display {} {
variable names
puts "My name is $names(first) $names(last)"
}
proc count {} {
common counter
return $counter
}
}
foo new name first Richard last Heinz
name destroy
set name [foo %AUTO% first Richard last Heinz]
name display
set name::names(first) George
name display
# generates an error, because it is an instance method
#foo display
$name destroyWhere common would behave like variable, with a static qualifier. I submit that a sequence of variable bar may be replaced by instance command that wraps all variable calls related to (instance) variables.
namespace class foo {
variable a
variable name
variable tool
variable logfile
proc __init__ ...
proc __destroy__ ...
proc display {{intologfile no}} {
instance ; # no need to invoke 'variable' again
if {$intologfile} {
puts $logfile "a=$a name=$name tool=$tool"
} else {
puts "a=$a name=$name tool=$tool"
}
}
...
}And a proc is a class method, until it invokes variable or instance commands, or uses an instance namespace qualifier. During instanciation, all namespace qualifiers equal to ::foo should be replaced by the instance's namespace qualifier, so that we can still use -textvariable Tk option.
namespace class foo {
variable label
proc __init__ {w} {
label $w.lbl -textvariable ::foo::label
pack $w.lbl
}
...
}The class name may instantiate objects by two methods:
foo new <instancename> <constructor_args> foo %AUTO% <constructor_args>
Any proc (without use of instance variables) could be called this way :
foo <myproc> <args>
The two special procs,
__init__ __destroy__
should throw an error when they are explicitly called.