Abbreviated form of incr Tcl, iTcl is the term used for referring to the object- oriented extensions meant for Tcl programming language. Let’s learn more about . The name is often written as “itcl” as that contains no metacharacters (i.e., space or brackets). BOOK Tcl/Tk Tools: contains an out of date tutorial for itcl. A more tutorial introduction is presented in the paper included with this distribution. See the class command for more details on creating and using classes.
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At times a method implementation may wish to know if it is the last method in a method chain and if not, what method implementation will be invoked next. As you can see, the object command and its namespace name no longer match.
We have created an object of class Derived that inherits from two parent classes, all of which define a method m. Throughout this chapter we have seen that when a method is invoked on an object, the code implementing the method for that object may come from several different places – the object, its class or an ancestor, a mixin, forwarded methods, filters or even unknown method handlers.
This is where tutorual next can help.
For these reasons, mixins seemed a better choice in our design aside from the fact that we needed some example to illustrate mixins. There is also a info class call itcll that works with classes instead of objects.
The author uses mixed case for data members to avoid conflicts with names of method arguments and local variables. How would we do this? As seen above, this command will only return objects that directly belong to the specified class, not if the class membership is inherited.
So the deposit method we saw earlier calls the UpdateBalance method as:. However some care should be taken when modifying a class since existing objects may not hold all state expected by the new class. Any operation on a destroyed object will naturally result in an error. Applications ihcl with Tcl Tk have the ability of coming together with great ease.
From Wikipedia, the free encyclopedia. Obj81 saving account data to database.
From a method context, the self call command returns similar information while self next identifies the next method itccl in the chain. Thus the above command will not show the variable Balance as that was defined in the base class Accountnot in SavingsAccount. The last known release of iTcl provides enhanced performance as well as a host of different features such as: Further declarations will extend or modify the class behaviour.
Although not required in our example, it should be noted that variables defined in the class are not automatically visible in object-specific methods. Now let us define another class that also uses the mixin. Retrieving the method chain The info class call command retrieves the method chain for a method.
Incr Tcl – Wikipedia
It all works now because we only call next if there is in fact a next method to call. The actual functionality is immaterial but it is intended to be fairly general purpose for example, logging or tracing and mixable into any class. For enumerating the classes mixed-in with an object, use info object mixinsanalogous to info class mixins.
Practically nothing about a class is sacred – you can add or delete methods, data members, change superclasses or mixins, and so on.
Object Oriented Programming in Tcl
Base method unknown unknown:: So we come up tutogial a new type of account, a Cash Management Account CMAwhich combines the features of the checking and brokerage accounts.
As before, we can also restrict the classes returned by specifying a pattern that the name must match.
We reiterate that not every method tutoriwl the chain is automatically invoked. Thus in our banking example, we may define separate classes representing savings accounts and checking accounts, each inheriting from the base account and therefore having a balance and methods for deposits and withdrawal. At the same time it is a class and hence must be an instance of oo:: The other piece of information that is provided inside a filter method is about the filter itself and is available through the self filter command.
There are several ways we could implement this but our preference in this case is for mix-ins over the alternatives for reasons we discuss later. The created objects are Tcl commands and as such can be created in any namespace.