[Xotcl] XOTcl 1.5.0 available
Gustaf Neumann
neumann at wu-wien.ac.at
Thu Sep 14 10:35:47 CEST 2006
Dear XOTcl community,
I am pleased to announce the availability of XOTcl 1.5.0.
To sum up, the biggest change is the introduction of slots objects,
which generalize the handling of "parameters" and object class
relations (like e.g. mixins). Slots provide a general and extensible
interface for changing properties of objects and classes. Every
multi-valued slot has e.g. a "<slot> add ..." method to add values
like previously only possible for mixin and filters. Slots contain
as well support for partial and lazy initialization of objects
(important, when e.g. variables are initialized through costly SQL
commands).
Another important change is that it is now possible to attach
the predefined methods of xotcl to arbitrary objects/classes.
For example, the XOTcl class system is created on the C-level
completely without any methods, all methods are attached from
the script initializing XOTcl.
I would like to thank the XOTcl community for many fruitful
inputs and discussions, that contribute significantly to the
development of XOTcl.
Best regards
-gustaf neumann
=================================================
Announcing XOTcl 1.5.0
*************************
Hi everybody. We are pleased to announce the availability of XOTcl 1.5.0.
Major changes relative to 1.4.0 are:
* Improved Functionality
+ The C-level implementation of XOTcl creates now the basic
classes ::xotcl::Object and ::xotcl::Class completely without
any methods. All predefined methods are now registered from
the initialization script-code (predefined.xotcl) via the new
command
::xotcl::alias <class>|<obj> <methodName> \
?-objscope? ?-per-object? <cmdName>
which is used for registering predefined Tcl commands as
methods. These aliases are like zero cost forwarders, since
they lookup the function pointer from the commands and used
these in the methods.
This change makes it possible to register the same command
on different classes (with maybe different names), such that
for example the predefined set method of ::xotcl::Object can
be replaced with a different method and the set method can
be registered on some other classes (maybe some application
classes).
This change makes it as well quite easy to develop some
other object oriented languages based on the XOTcl
framework, since all methods can be rearrange from the Tcl
layer .
+ Slots
A slot is a meta-object that manages property-changes of
objects. A property is either an attribute or a role of an
relation.
In a nutshell, a slot has among other attributes
- a name (which it used to access it),
- a domain (object or class on which it can be used) , and
- can be multivalued or not
Every slot defines a uniform interface to access its
content. So has for example, every multivalued slot a
method "add" to add a value to the list of values and a
method "remove" to remove it again.
We distinguish between system slots (predefined slots like
class, superclass, mixin, instmixin, filter, instfilter) and
application slots (e.g. attributes of classes).
System Slots
========
System slots are predefined slots defining e.g. some relations
between classes, or between objects and classes.
The predefined system slots are:
- superclass: every class in XOTcl has one or more superclasses.
The name of this slot is "superclass", the domain is
"::xotcl::Class",
the slot is multivalued. One object might have multiple
superclasses.
- class: every object has a class; therefore, the domain of the
slot
is "::xotcl::Class", the property is not multivalued.
- mixin: every object in XOTcl can have one or more mixin classes.
The name of this slot is "mixin", the domain is
"::xotcl::Object", the slot is
multivalued.
- instmixin: same as above, but the domain is "::xotcl::Class"
- filter, instfilter: similar to "mixin" and "instmixin"
Every slot can be used set and query the property from its domain.
The syntax for setting values is
<object> <property> newValue
and for getting its values is
set x [<object> <property>]
Every multivalued slot has as well a method "add" and "remove"
Examples for using the system slot "mixin"
Object o; Class M; class N
o mixin ::M ;# replacing the per-object mixins of o
with M
o mixin add ::N ;# add N to the front of the mixin list
o mixin delete ::M ;# delete M from the mixin list
puts [o mixin] ;# query the current mixin list
Attribute Slots
=========
Attribute slots are used to manage the setting and querying
of instance variables. We define now a person with three
attributes,"name", "salary" and "projects".
Class Person -slots {
Attribute name
Attribute salary -default 0
Attribute projects -default {} -multivalued true
}
Examples for using the slots are
Person p1 -name "Joe"
p1 projects add project1
Some additional features of the slots are:
- Support for value checking for
* primitive types (all types from "string is", like integer,
boolean, ...)
* instances of Classes (e.g. value must be an instance
of Person)
* custom value checkers
* uniform interface for single and multi-valued slots
- Support for lazy initialization (e.g. when costly
commands (like SQL) are used to initialize instance
variables, not all variables are used for each object)
- more experimental low level functionality, like
* initcmd (executed, whenever the variable is read the
first time)
* valuecmd (executed, whenever the variable is read)
* valuechangedcmd (executed, whenever the variable is
altered)
For more details, see
http://media.wu-wien.ac.at/doc/tutorial.html#slots
+ Re-implementation of the method "parameter" based on slots.
All forms except
... -parameter {name1 {name2 default2}} ...
(I.e. pure accessor parameters and parameters with
defaults) are deprecated, since slots are the much more
powerful and orthogonal construct.
The old c-based parameter support based on "parameterclass"
is deprecated. It is still in the C-code (the method "parameter"
is redefined in predefined.xotcl). If someone urgently needs
it, please remove the parameter instproc from predefined
for the time being, and write an email to me, in case
you really need it). The C code for parameter will be removed
in the next release.
+ Improved introspection though the procsearch method. This
method reports now in its second argument not only
[inst]proc but as well [inst]forward, [inst]parametercmd
and [inst]cmd (the latter for methods implemented in C.
* Improved introspection through "info"
- new subcommand "info slots"
- implemented backwards bug-compatible "info parameter",
deprecated
+ Improved serializer
- better handling of cyclical dependencies, when mixins are
involved
- fix for namespace handling to make the XOTcl communication
library classes working with the aolserver (thanks for
Stefan Sobernig
for pointing this out)
- Now other ::xotcl::* objects can be included in the
aolserver blueprint
(e.g. non positional argument handlers)
- handling of slot dependencies
- more convenient calling of the serializer:
Method "serialize" for Object is defined when the package
xotcl::serializer
is loaded.
+ Improved forwarding commands
- New option for the argument substitution. When the argument
list of the forward command contains "%argclindex {a b
c}", then
depending of the number of arguments at invocation "a", "b"
or "c" is substituted. If more arguments are used at the
invocation
of the forwarder than values are contained in the list
after %argclindex,
an error is generated.
- New options for forwarder:
* The option -earlybinding can be used to look
up the function pointer of the called Tcl command at
definition time of the forwarder instead of invocation
time.
This option should only be used for calling
C-implemented Tcl commands)
* The option -verbose prints the substituted command in
the forwarder
prior to invocation.
+ New snit-like utility functions:
- ::xotcl::myvar varName: return the fully qualified
variable name
of the specified variable.
- ::xotcl::myproc methodName ?args?: call an xotcl method
without the need
of using "[list [self] methodName ...]"
Both commands are namespace exported
+ added "subst" to the set of Tcl imported methods (like e.g.
incr, append, ...)
On can do now:
% Object o
::o
% o subst {I am [self]}
I am ::o
+ added new method for ::xotcl::Object named "contains":
This method is essentially a value added back-port
of the OpenACS version. It allows to create a nested
object structure with little syntactic overhead. See tutorial
or language reference for more details.
* Improved code quality:
+ fixed a bug with nonpositional arguments, some
positional arguments and "args"
+ fixed a bug in nonpositional arguments when called without
arguments
+ tested with Tcl 8.4.13 and 8.5a4
+ improved error messages in connection with nonpositional arguments
+ fixed a bug in the xotcl trace module (many thanks to jima for
reporting)
+ fixed a namespace bug in ::xotcl::package require in connection
with xotclide
(many thanks to Bill Paulsen and Artur Trzewik for
identifying the problem and
suggesting a fix)
+ improved documentation (e.g. new sections added,
some sections deleted, spelling improved, in total 8 pages
longer)
+ fixed documentation bugs (many thanks for Kristoffer for reporting)
+ more regression tests added
For more details about the changes, please consult the ChangeLog and
documentation.
MORE INFO
General and more detailed information about XOTcl and its components
can be found at http://www.xotcl.org
Best regards,
Gustaf Neumann
Uwe Zdun
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