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 BOOK Tcl/Tk Tools: contains an out of date tutorial for itcl.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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Lists all methods defined and exported by CheckingAccount itself Lists both exported and private methods defined by CheckingAccount Lists all methods defined and exported by Tutorlalits ancestors, or mixins Lists both exported and private methods defined by CheckingAccountits ancestors, or mixins Lists exported and non-exported methods defined in the object itself.
It is marked as a filter method using the filter command.
We have already discussed all these in detail in an earlier section. The method whose definition is being retrieved has to be defined in the specified class, not in an ancestor or a class that is mixed into the specified class.
This ability to define object-specific methods can be very useful. The other piece of information that is provided inside a filter method is about the filter itself and is available through the self filter jtcl.
Object Oriented Programming in Tcl
The self class command will fail when called from a method defined directly on an object since there is no class associated with the method in that case. If the derived class does define a constructor, that is invoked instead and it is up to that constructor to call the base class constructor using next as appropriate. Short form of incr Tcl, iTcl is simply a set of object-oriented extensions meant for the Tcl programming language. Smith is suspected of being up to his old tricks again and we need to monitor his accounts and log all activity.
The listed variables are only those defined through the variable statement for that itcp class.
Data members in derived classes Derived classes can define new data members using either variable in the class definition or my variable within a method as in withdraw. We will not worry about how this is done but just assume some global procedures are available for the purpose.
Note the optional form of the oo:: Whether a method occuring in the list is actually called or not will depend on preceding methods passing on the invocation via icl next command.
itcl (n) – Linux Man Pages
This is detail as it maintains the same itcl programmer interface. For enumerating variables for an object as opposed to a class, there are two commands: Thus the checking object automatically supports the new functionality.
Not commonly used in operational code, this ability to destroy classes is sometimes useful during interactive development and debugging to reset to a known clean state. The class Account is actually just another Tcl command and could have been created in any namespace we choose, not necessarily the global one.
The actual functionality is immaterial but it is intended to be fairly general purpose for example, logging or tracing and mixable into any class. As expected, the unknown methods, where defined, are called. Conceptually, the class does not represent an objectbut rather a capability or, as is termed in some literature, a role.
[incr Tcl] – Object-Oriented Programming in Tcl/Tk
The info class call command retrieves the method chain for a method. No value judgement intended. As you can see, the object command and its namespace name no longer match. The home page is http: The returned list contains two interesting elements:. See the Tcl tuotrial for the oo:: However, Tcl being Tcl, it is always possible to add a variable access capability using the fact that each object has a private namespace that can be retrieved through introspection.
Working with objects Having defined our model, we can now begin operation of our bank to illustrate how objects are used. These differ from normal methods in only two respects:. Many times, the filter method needs to know what method the caller is actually trying to invoke.
Classes and objects can override the default implementation method to take some ltcl action instead. Introspecting class relationships The info class superclasses command returns the direct superclasses of a class.
Furthermore, the list of applications depending ttorial the incr Tcl is tutorlal growing day by day. The following code snippet will crash Tcl versions prior to 8. This would have accomplished the same job in a clearer manner. Constructors and destructors There is one final thing we need to do before we can start banking operations and that is to provide some means to initialize an Account object when it is created and perform any required clean itc when it is destroyed.
Any method invocation on the object will then result in the filter method being invoked first. The self command is only usable within a method and returns the name of the current object when called without parameters. Filters could be replaced by other techniques such as overriding and ictl chaining methods.
Note that modifying the class definition in any manner, in this case adding a mixin, also impacts existing objects of that class.