./doc/langRef.xotcl
./doc/langRef.xotcl
| Description: | XOTcl language reference. Describes predefined objects and classes. |
| Predefined primitives: |
XOTcl contains three predefined primitives:
self computes callstack related information. It can be used in the following ways:
my someMethod is a short form for [self] someMethod and can only be called in a context of an instproc or an method specific proc. It allows certain optimizations and shorter to write. next executes the "next" method on the precedence order and return with the result. |
| Date: | $Date: 2004/07/02 11:22:31 $ |
| Description: | This meta-class holds the pre-defined methods available for all XOTcl classes. |
| Arguments: | obj: new obj/class name |
| ?args?: arguments passed to the new class after creation | |
| Description: | Allocate memory for a new XOTcl object or class. create uses alloc to allocate memory. But create also calls init and evaluates '-' arguments as method calls. In seldom cases the programmer may want to suppress the create mechanism and just allocate memory. Then alloc can be used. |
| Return: | new class name |
| Arguments: | objName: name of a new class or object |
| ?args?: arguments passed to the constructor | |
| Description: |
Create user-defined classes or objects. If the class is a meta-class,
a class is created, otherwise an object.
Create firstly calls alloc in order to allocate memory for the
new object. Then default values for parameters are searched on
superclasses (an set if found). Then args is searched for args
starting with '-' followed by an alpha character. These arguments
are called as methods. '-' followed by a numerical is interpreted
as a negative number (and not as a method). If a value of a method
called this way starts with a "a", the call can be placed safely
into a list (e.g. "Class c [-strangearg -a-] -simplearg 2").
Finally the constructor init is called on the object
with all arguments up to the first '-' arg. The create method is called implicitly through the unknown mechanism when a class (meta-class) is called with an unknown method. E.g. the following two commands are equivalent Car herby -color red
Car create herby -color red
When a users may want to call the constructor init
before other '-' methods, one can specify '-init'
explicitly in the left to
right order of the '-' method. Init is called always only once.
e.g.: Class Car -init -superclass Vehicle |
| Return: | name of the created instance (result of alloc) |
| Arguments: | args: info options |
| Description: |
Introspection of classes. All options available for objects
(see info object) is also available
for classes.
The following options can be specified:
|
| Return: | Value of introspected option as a string. |
| Arguments: | obj: obj/class name |
| ?args?: arguments passed to the destructor | |
| Description: |
Standard destructor. Destroys XOTcl object physically from the memory.
Can be overloaded for customized destruction process.
In XOTcl objects are not directly destroyed, when a destroy is encountered in a method. Beforehand, the interpreter looks up whether the object is still referenced on the method callstack or not. If not, the object is directly destroyed. Otherwise every occurrence of the object on the callstack is marked as destroyed. During popping of the callstack, for each object marked as destroyed, the reference count is decremented by one. When no more references to the object are on the callstack the object is physically destroyed. This way we can assure that objects are not accessed with [self] in running methods after they are physically destroyed. |
| Return: | empty string |
| Arguments: | filterList: list of methods that should be registered as filters |
| Description: | Specifies the list of filters registered for the class. instfilter overwrites all previous setting. Filters must be available on the class or its heritage order. Filters may also reside on the meta-class of the class. Filter list may contain filter guards. Then the filter is composed of two list elements: {filtername filterguard}. |
| Return: | empty string |
| Arguments: | filterList: name of the new instfilter |
| Description: | Convenience method that appends an instfilter to the existing filters of the class. |
| Return: | empty string |
| Arguments: | filtername: filter name of a registered filter |
| guard: set of conditions to execute the filter | |
| Description: | Add conditions to guard a filter registration point. The filter is only executed, if the guards are true. Otherwise we ignore the filter. If no guards are given, we always execute the filter. |
| Return: | empty string |
| Arguments: | invariantList: Body of invariants for the class |
| Description: | Specify invariants for the class. These are inherited by sub-classes. The invariants must hold for all instances. All assertions are a list of ordinary Tcl conditions. |
| Return: | empty string |
| Arguments: | instmixinList: list of classes that should be registered as instmixins |
| Description: | Specifies the list of instmixins (per-class mixins) for the class. Note that the registration of a per-mixin-class does not invoke automatically the constructors of the registered class. The method instmixin overwrites any previous settings. |
| Return: | empty string |
| Arguments: | mixinList: name of the new instmixin |
| Description: | Convenience method that appends an instmixin to the existing mixins of the class. |
| Return: | empty string |
| Arguments: | name: variable to be provided with getter/setter method |
| Description: |
Add a getter/setter command for an instance variable with the
specified name. This method is used for example by the
parameter method.
Example: Class C C instparametercmd x C c1 -x 100 puts [c1 x] |
| Return: | empty string |
| Arguments: | name: instance method name |
| args: instance method arguments | |
| body: instance method body | |
| ?preAssertion?: optional assertions that must hold before the proc executes | |
| ?postAssertion?: optional assertions that must hold after the proc executes | |
| Description: | Specify an instance method in the same style as Tcl specifies procs. Optionally assertions may be given. The number of args is either 3 or 5. Therefore, to specify only post-assertions an empty pre-assertion list must be given. All assertions are a list of ordinary Tcl conditions. |
| Return: | empty string |
| Arguments: | name: cmd to be execute in obj scope |
| Description: | Create a method 'name' that is evaluated as a tcl command in the scope of the object. E.g. 'Object insttclcmd vwait' creates an instproc vwait on Object that executes Tcl's vwait in the scope of the object. That is local vars of the object are accessible to that vwait. (Used to circumvent, for instance, the TCL_GLOBAL_ONLY flag of vwait in Tcl.) |
| Return: | empty string |
| Arguments: | ?-childof obj? ?args?: args passed to create |
| Description: |
Convenience method to create an autonamed object. E.g.:
Http newcreates ::xotcl::__#0, a subsequent call creates ::xotcl::__#1, ... If -childof obj is specified, the new object is created as a child of the specified object. |
| Return: | new object name |
| Arguments: | parameterList: list of parameter definitions |
| Description: |
Specify parameters automatically created for each instance.
Parameters denote instance variables which are available on each class instance
and that have a getter/setter method with their own name.
Parameters are specified in a parameter list of the form
{p1 p2 ... pn}.
p1 ... pn may either be parameter names or definitions of the form
{parameterName defaultValue}.
If a default value is given, that parameter
is created during creation process of the instance object, otherwise
only the getter/setter method is created (and the parameter does not
exist). The getter/setter method has the same name as the
parameter. It gets and returns the parameter, if no
argument is specified. With one argument, the parameter is set
to the argument value.
Example:
Class Car -parameter {{doors 4} color}
Car herby -doors 2 -color green
|
| Return: | empty string |
| Arguments: | class: parameter class name |
| Description: |
Set the parameter class.
The parameter class specifies how parameters are stored and
maintained internally. Per default, a method "default" is called,
to set the parameter with a default value.
I.e.,
Class Car -parameter {
{doors 4}
}
is a short form for
Class Car -parameter {
{doors -default 4}
}
For specialized parameter classes other methods can be called, e.g.
{doors -default 3 -updateWidget car}
|
| Return: | empty string |
| Arguments: | obj: obj to be recreated |
| ?args?: arbitrary arguments | |
| Description: | Hook called upon recreation of an object. Performs standard object initialization, per default. May be overloaded/-written. It calls another method cleanup which handles actual cleanup of the object during next. That means, if you overload recreate, in the pre-part the object still contains its old state, after next it is cleaned up. |
| Return: | obj name |
| Arguments: | classList: list of classes |
| Description: | Specify super-classes for a class. "superclass" changes the list of superclasses dynamically to classList. |
| Return: | empty string |
| Arguments: | ?args?: arbitrary arguments |
| Description: |
Standard unknown mechanism. This mechanism is always triggered when
XOTcl does not know a method called on an object. Supposed that
there is no method with the called name, XOTcl looks up the method
"unknown" (which is found on the Class Object) and executes it.
The standard unknown-mechanism of XOTcl calls create with all
arguments stepping one step to the right; in the general case:
ClassName create ClassName ?args?Unknown can be overloaded in user-defined subclasses of class. |
| Return: | Standard unknown mechanism returns result of create |
| Arguments: | : |
| Description: | This method is used to specify that the object should be deleted automatically, when the current tcl-proc/object-proc/instproc is left. Example set x [Object new -volatile] |
| Return: | empty string |
| Arguments: | name: name of class to be created |
| Description: | This method is called, whenever XOTcl references a class, which is not defined yet. In the following example: Class C -superclass D D is not defined. Therefore Class __unknown D is called. This callback can be used to perform auto-loading of classes. After this call, XOTcl tries again to resolve D. If it succeeds, XOTcl will continue; otherwise, an error is generated. |
| Return: | empty string |
| Description: | This class holds the pre-defined methods available for all XOTcl objects. All these methods are also available on classes. |
| Arguments: | methtype: instproc or proc |
| methname: name of abstract method | |
| arglist: arguments | |
| Description: | Specify an abstract method for class/object with arguments. An abstract method specifies an interface and returns an error, if it is invoked directly. Sub-classes or mixins have to override it. |
| Return: | error |
| Arguments: | varName: name of variable |
| args: arguments to append | |
| Description: | Append all of the value arguments to the current value of variable varName. Wrapper to the same named Tcl command (see documentation of Tcl command with the same name for details). |
| Return: | empty string |
| Arguments: | opt: array option |
| array: array name | |
| ?args?: args of the option | |
| Description: | This method performs one of several operations on the variable given by arrayName. It is a wrapper to the same named Tcl command (see documentation of Tcl command with the same name for details). |
| Return: | diverse results |
| Arguments: |
?<-instance>|<-reset>?: Optional modifiers: '-instance' makes the autoname start with a small letter. '-reset' resets the autoname index to 0. |
| name: base name of the autoname | |
| Description: |
autoname creates an automatically assigned name. It is
constructed from the base name plus an index, that is
incremented for each usage. E.g.:
$obj autoname aproduces a0, a1, a2, ... Autonames may have format strings as in the Tcl 'format' command. E.g.: $obj autoname a%06dproduces a000000, a000001, a000002, ... |
| Return: | newly constructed autoname value |
| Arguments: | options: none, one or more of: (?all? ?pre? ?post? ?invar? ?instinvar?) |
| Description: |
Turn on/off assertion checking. Options argument is the list
of assertions, that should be checked on the object automatically.
Per default assertion checking is turned
off. Examples:
o check {}; # turn off assertion checking on object o
o check all; # turn on all assertion checks on object o
o check {pre post}; # only check pre/post assertions
info check introspects check options.
|
| Return: | empty string |
| Arguments: | newClass: new class name |
| Description: | Changes the class of an object dynamically to newClass. |
| Return: | empty string |
| Arguments: | ?args?: Arbitrary arguments passed to cleanup |
| Description: | Resets an object or class into an initial state, as after construction. Called during recreation process by the method 'recreate' |
| Return: | empty string |
| Arguments: | ?args?: '-' method calls |
| Description: |
Calls the '-' methods. I.e. evaluates arguments and calls
everything starting with '-' (and not having a digit a
second char) as a method. Every list element until the next '-'
is interpreted as a method argument. configure is called
before the constructor during initialization and recreation.
E.g. Object o -set x 4here: o configure -set x 4is executed. |
| Return: | number of the skipped first arguments |
| Arguments: | newName: destination of copy operation |
| Description: | Perform a deep copy of the object/class (with all information, like class, parameter, filter, ...) to "newName". |
| Return: | empty string |
| Arguments: | ?args?: Arbitrary arguments passed to the destructor |
| Description: |
Standard destructor.
Can be overloaded for customized destruction process. Actual destruction
is done by instdestroy. "destroy" in principal does:
Object instproc destroy args {
[my info class] instdestroy [self]
}
|
| Return: | empty string |
| Arguments: | args: cmds to eval |
| Description: | Eval args in the scope of the object. That is local variables are directly accessible as Tcl vars. |
| Return: | result of cmds evaled |
| Arguments: | al: Argument List Name |
| name: Name of the Configure Argument to be extracted (should start with '-') | |
| ?cutTheArg?: if cutTheArg not 0, it cut from upvar argsList, default is 0 | |
| Description: | Check an argument list separated with '-' args, as for instance configure arguments, and extract the argument's values. Optionally, cut the whole argument. |
| Return: | value list of the argument |
| Arguments: | var: variable name |
| Description: | Check for existence of the named instance variable on the object. |
| Return: | 1 if variable exists, 0 if not |
| Arguments: | filterList: list of methods that should be registered as filters |
| Description: | Specifies the list of filters registered for the class. filter overwrites all previous setting. Filters must be available on the class or its heritage order. Filters may also reside on the meta-class of the class. Filter list may contain filter guards. Then the filter is composed of two list elements: {filtername filterguard}. |
| Return: | empty string |
| Arguments: | filterList: name of the new filter |
| Description: | Convenience method that appends a filter to the existing filters of the object. |
| Return: | empty string |
| Arguments: | filtername: filter name of a registered filter |
| guard: set of conditions to execute the filter | |
| Description: | Add conditions to guard a filter registration point. The filter is only executed, if the guards are true. Otherwise we ignore the filter. If no guards are given, we always execute the filter. |
| Return: | an empty string |
| Arguments: | methodName: filter method name |
| Description: | Search a full qualified method name that is currently registered as a filter. Return a list of the proc qualifier format: 'objName|classname proc|instproc methodName'. |
| Return: | full qualified name, if filter is found, otherwise an empty string |
| Arguments: | ?className?: name of a class to be tested |
| Description: | Test whether the argument is either a mixin or instmixin of the object or if it is on the class hierarchy of the object. This method combines the functionalities of istype and ismixin. |
| Return: | 1 or 0 |
| Arguments: | varName: variable name |
| ?increment?: value to increment | |
| Description: | Increments the value stored in the variable whose name is varName. The new value is stored as a decimal string in variable varName and also returned as result. Wrapper to the same named Tcl command (see documentation of Tcl command with the same name for details). |
| Return: | new value of varName |
| Arguments: | args: info options |
| Description: |
Introspection of objects. The following options can be specified:
|
| Return: | Value of introspected option as a string. |
| Arguments: | v1: instvar variable |
| ?v2...vn?: optional other instvar variables | |
| Description: |
Binds an variable of the object to the current method's scope.
Example:
kitchen proc enter {name} {
my instvar persons
set persons($name) [clock seconds]
}
Now persons can be accessed as a local variable of the method.A special syntax is: {varName aliasName} . This gives the variable with the name varName the alias aliasName. This way the variables can be linked to the methods scope, even if a variable with that name already exists in the scope. |
| Return: | empty string |
| Arguments: | invariantList: Body of invariants for the object |
| Description: | Specify invariants for the objects. All assertions are a list of ordinary Tcl conditions. |
| Return: | empty string |
| Arguments: | ?className?: name of a class to be tested |
| Description: | Test whether the argument (or the Object, if no argument is specified) is an existing class or not. |
| Return: | 1 or 0 |
| Arguments: | ?metaClassName?: name of a metaclass to be tested |
| Description: | Test whether the argument (or the Object, if no argument is specified) is an existing metaclass or not. |
| Return: | 1 or 0 |
| Arguments: | ?className?: name of a class to be tested |
| Description: | Test whether the argument is a mixin or instmixin of the object. |
| Return: | 1 or 0 |
| Arguments: | objName: string that should be tested, whether it is a name of an object or not |
| Description: | Test whether the argument is an existing object or not. Every XOTcl object has the capability to check the object system. |
| Return: | 1 or 0 |
| Arguments: | className: type name |
| Description: | Test whether the argument is a type of the object. I.e., 1 is returned if className is either the class of the object or one of its superclasses. |
| Return: | 1 or 0 |
| Arguments: | varName: name of variable |
| args: elements to append | |
| Description: | Append all the specified arguments to the list specified by varName as separated elements (typically separated by blanks). If varName doesn't exist, it creates a list with the specified values (see documentation of Tcl command with the same name for details). |
| Return: | empty string |
| Arguments: | mixinList: list of classes that should be registered as mixins |
| Description: | Specifies the list of mixins registered for the object. The method mixin overwrites all previous settings. |
| Return: | empty string |
| Arguments: | mixinList: name of the new mixin |
| Description: | Convenience method that appends a mixin to the existing mixins of the object. |
| Return: | empty string |
| Arguments: | newName: destination of move operation |
| Description: | Perform a deep move of the object/class (with all information, like class, parameter, filter, ...) to "newName". |
| Return: | empty string |
| Arguments: | name: variable to be provided with getter/setter method |
| Description: |
Add a getter/setter for an instance variable with the
specified name as a command for the obj.
Example: Object o o parametercmd x o x 100 puts [o x] |
| Return: | empty string |
| Description: |
flag that constructor (method init) should
not be called.
Example: Class C C instproc init {} {puts hu} C c1 -noinit The object c1 will be created without calling the constructor. This can be used to draw a snapshot of an existing object (using the serializer) and to recreate it in some other context in its last state. |
| Return: | empty string |
| Arguments: | name: method name |
| args: method arguments | |
| body: method body | |
| ?preAssertion?: optional assertions that must hold before the proc executes | |
| ?postAssertion?: optional assertions that must hold after the proc executes | |
| Description: | Specify a method in the same style as Tcl specifies procs. Optionally assertions may be given. The number of args is either 3 or 5. Therefore, to specify only post-assertions an empty pre-assertion list must be given. All assertions are a list of ordinary Tcl conditions. |
| Return: | empty string |
| Arguments: | procname: simple proc name |
| Description: |
Search for a proc or instproc on an object and return the fully
qualified name of the method as a list in
proc qualifier format:
'objName|classname proc|instproc methodName'. E.g.,
o procsearch setreturns ::xotcl::Object instproc set. |
| Return: | fully qualified name of the searched method or empty string if not found |
| Description: | The method requireNamespace can be used to ensure that the object has a namespace. Namespaces are created automatically by XOTcl, when e.g. an object has child objects (aggregated objects) or procs. The namespace will be used to keep instance variables, procs and child objects. To check, whether an object currently has a namespace, info hasNamespace can be used. Hint: In versions prior to XOTcl 0.9 all XOTcl objects had their own namespaces; it was made on demand to save memory when e.g. huge numbers of objects are created. requireNamespace is often needed when e.g. using Tk widgets when variables are to be referenced via the namespace (with ... -variable [self]::varname ...). |
| Return: | empty string |
| Arguments: | varname: name of the instance variable |
| ?value?: optional new value | |
| Description: | Set an instance variable in the same style as Tcl sets a variable. With one argument, we retrieve the current value, with two arguments, we set the instance variable to the new value. |
| Return: | Value of the instance variable |
| Arguments: | varName: name of variable |
| Description: | Trace an object variable (see documentation of Tcl command with the same name for details). |
| Return: | empty string |
| Arguments: | v1: Variable to unset |
| ?v2...vn?: Optional more vars to unset | |
| Description: | The unset operation deletes one or optionally a set of variables from an object. |
| Return: | empty string |
| Arguments: | ?level?: Level |
| command ?args?: command and arguments to be called | |
| Description: |
When this method is used without the optional level, it is a short form
of the Tcl command upevel [self callinglevel] command ?args?. When it is called with the level, it is compatible with the original tcl command. |
| Return: | result of the command |
| Arguments: | ?level?: Level |
| othervar localvar: referenced variable and variale in the local scope | |
| ?othervar localvar?: optional pairs of referenced and local variable names | |
| Description: |
When this method is used without the optional level, it is a short form
of the Tcl command upvar [self callinglevel] othervar localvar ?...?. When it is called with the level, it is compatible with the original tcl command. |
| Return: | result of the command |
| Arguments: | varName: name of variable |
| Description: | Enter event loop until the specified variable is set (see documentation of Tcl command with the same name for details). |
| Return: | empty string |
| Description: | Retrieve the current exit handler procedure body as a string. |
| Return: | exit handler proc body |
| Arguments: | body: procedure body |
| Description: | Set body for the exit handler procedure. The exit handler is executed when XOTcl is existed or aborted. Can be used to call cleanups that are not associated with objects (otherwise use destructor). On exit the object destructors are called after the user-defined exit-handler. |
| Return: | exit handler proc body |
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