my manual page - TclOO Commands

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NAME

my, myclass — invoke any method of current object or its class

SYNOPSIS

package require tcl::oo

my methodName ?arg ...?
myclass methodName ?arg ...?

The my command is used to allow methods of objects to invoke methods of the object (or its class), and the myclass command is used to allow methods of objects to invoke methods of the current class of the object as an object. In particular, the set of valid values for methodName is the set of all methods supported by an object and its superclasses, including those that are not exported and private methods of the object or class when used within another method defined by that object or class.

The object upon which the method is invoked via my is the one that owns the namespace that the my command is contained in initially (NB: the link remains if the command is renamed), which is the currently invoked object by default. Similarly, the object on which the method is invoked via myclass is the object that is the current class of the object that owns the namespace that the myclass command is contained in initially. As with my, the link remains even if the command is renamed into another namespace, and defaults to being the manufacturing class of the current object.

Each object has its own my and myclass commands, contained in its instance namespace.

EXAMPLES

This example shows basic use of my to use the variables method of the oo::object class, which is not publicly visible by default:

oo::class create c {
    method count {} {
        my variable counter
        puts [incr counter]
    }
}

c create o
o count              → prints "1"
o count              → prints "2"
o count              → prints "3"

This example shows how you can use my to make callbacks to private methods from outside the object (from a trace), using namespace code to enter the correct context. (See the callback command for the recommended way of doing this.)

oo::class create HasCallback {
    method makeCallback {} {
        return [namespace code {
            my Callback
        }]
    }

    method Callback {args} {
        puts "callback: $args"
    }
}

set o [HasCallback new]
trace add variable xyz write [$o makeCallback]
set xyz "called"     → prints "callback: xyz {} write"

This example shows how to access a private method of a class from an instance of that class. (See the classmethod declaration in oo::define for a higher level interface for doing this.)

oo::class create CountedSteps {
    self {
        variable count
        method Count {} {
            return [incr count]
        }
    }
    method advanceTwice {} {
        puts "in [self] step A: [myclass Count]"
        puts "in [self] step B: [myclass Count]"
    }
}

CountedSteps create x
CountedSteps create y
x advanceTwice       → prints "in ::x step A: 1"
                     → prints "in ::x step B: 2"
y advanceTwice       → prints "in ::y step A: 3"
                     → prints "in ::y step B: 4"
x advanceTwice       → prints "in ::x step A: 5"
                     → prints "in ::x step B: 6"
y advanceTwice       → prints "in ::y step A: 7"
                     → prints "in ::y step B: 8"

KEYWORDS

method, method visibility, object, private method, public method