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Multiple classes and inheritance demonstration
[incr-Tcl] example from a Well House Consultants training course
More on [incr-Tcl] [link]
Source code: exv Module: T245
package require Itcl
namespace import itcl::* set comment { # A neat way of doing a block comment in Tcl! Incr-Tcl is an excellent Object Oriented Extension to Tcl, with all the usual OO facilities supported. This example pulls many of the various elements together in a single short demonstration. You MAY have an incr-Tcl executable on your system, or you may need to load the extra facilities in as a package - see above. If you load as a package, then this is an excellent use of a namespace import since you really won't want to be writing itcl::class each time you define a class, will you? } # Here's an example of a base class: class getabout { variable operator public variable miles method getopo {} { return "$operator !!!!! " } } # A class that inherits from that base class: class dublintram { inherit getabout constructor {whom} { set operator $whom} method getprice {} {return 0} } # A second class that inherits from that base class: class pts { inherit getabout variable departure variable reliability variable pencepermile constructor {opo time rel ppm {mls 0}} { set operator $opo set departure $time set reliability $rel set pencepermile $ppm set miles $mls } method getprice {} { return [expr $miles * $pencepermile] } method getpencepermile {} { return $pencepermile } method setpencepermile {newval} { set pencepermile $newval } } # MAIN CODE ------------------- # Some slightly contrived code to set up a series of # objects - in a real application, we would probably # have a loop reading from a file of database here! set c 1 pts place$c "East Midlands" 07:00 80 24 40 incr c pts place$c "First Great Western" 07:17 50 21 25 incr c dublintram place$c Connex incr c pts place$c FGW 07:45 98 56 94 # Note that each of our objects has a name that's made up # of a pattern - place1 place2 place3 etc, which will allow # us to iterate through them later # A demonstration of running a method on an object (to set a value) # Note that creating an object was created a command of that same name place2 setpencepermile 50 # Loop though and report on all the objects: for {set k 1} {$k <= $c} {incr k} { # Run a method to get the price # This method is polymorphic - one for each class # and the code will run the APPROPRIATE method each time set costshim [place$k getprice] # Run a method to get the operator. # This method is the same each time - it has been # inherited in each case from the base class set runby [place$k getopo] # All itcl objects support configure and cget subcommands # cget allows you to read any public variables without having # to provide an accessor method for every one of them, and # configure lets you set the public variables without a method. set rb [place$k cget -miles] puts "$runby place$k - $costshim $rb" } Learn about this subject
This module and example are covered on the following public courses:
* Learning to program in Tcl * Tcl Programming * Tcl Programming Also available on on site courses for larger groups Books covering this topic
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