Tcl_Method(3) TclOO Library Functions Tcl_Method(3)______________________________________________________________________________NAME
Tcl_ClassSetConstructor, Tcl_ClassSetDestructor, Tcl_MethodDeclar‐
erClass, Tcl_MethodDeclarerObject, Tcl_MethodIsPublic, Tcl_MethodIs‐
Type, Tcl_MethodName, Tcl_NewInstanceMethod, Tcl_NewMethod, Tcl_Object‐
ContextInvokeNext, Tcl_ObjectContextIsFiltering, Tcl_ObjectCon‐
textMethod, Tcl_ObjectContextObject, Tcl_ObjectContextSkippedArgs -
manipulate methods and method-call contexts
SYNOPSIS
#include <tclOO.h>
Tcl_Method
Tcl_NewMethod(interp, class, nameObj, isPublic,
methodTypePtr, clientData)
Tcl_Method
Tcl_NewInstanceMethod(interp, object, nameObj, isPublic,
methodTypePtr, clientData)
Tcl_ClassSetConstructor(interp, class, method)
Tcl_ClassSetDestructor(interp, class, method)
Tcl_Class
Tcl_MethodDeclarerClass(method)
Tcl_Object
Tcl_MethodDeclarerObject(method)
Tcl_Obj *
Tcl_MethodName(method)
int
Tcl_MethodIsPublic(method)
int
Tcl_MethodIsType(method, methodTypePtr, clientDataPtr)
int
Tcl_ObjectContextInvokeNext(interp, context, objc, objv, skip)
int
Tcl_ObjectContextIsFiltering(context)
Tcl_Method
Tcl_ObjectContextMethod(context)
Tcl_Object
Tcl_ObjectContextObject(context)
int
Tcl_ObjectContextSkippedArgs(context)ARGUMENTS
Tcl_Interp *interp (in/out) The interpreter holding the object
or class to create or update a
method in.
Tcl_Object object (in) The object to create the method in.
Tcl_Class class (in) The class to create the method in.
Tcl_Obj *nameObj (in) The name of the method to create.
Should not be NULL unless creating
constructors or destructors.
int isPublic (in) A boolean flag saying whether the
method is to be exported.
Tcl_MethodType *methodTypePtr (in) A description of the type of the
method to create, or the type of
method to compare against.
ClientData clientData (in) A piece of data that is passed to
the implementation of the method
without interpretation.
ClientData *clientDataPtr (out) A pointer to a variable in which to
write the clientData value supplied
when the method was created. If
NULL, the clientData value will not
be retrieved.
Tcl_Method method (in) A reference to a method to query.
Tcl_ObjectContext context (in) A reference to a method-call con‐
text. Note that client code must
not retain a reference to a con‐
text.
int objc (in) The number of arguments to pass to
the method implementation.
Tcl_Obj *const *objv (in) An array of arguments to pass to
the method implementation.
int skip (in) The number of arguments passed to
the method implementation that do
not represent "real" arguments.
_________________________________________________________________DESCRIPTION
A method is an operation carried out on an object that is associated
with the object. Every method must be attached to either an object or a
class; methods attached to a class are associated with all instances
(direct and indirect) of that class.
Given a method, the entity that declared it can be found using
Tcl_MethodDeclarerClass which returns the class that the method is
attached to (or NULL if the method is not attached to any class) and
Tcl_MethodDeclarerObject which returns the object that the method is
attached to (or NULL if the method is not attached to an object). The
name of the method can be retrieved with Tcl_MethodName and whether the
method is exported is retrieved with Tcl_MethodIsPublic. The type of
the method can also be introspected upon to a limited degree; the func‐
tion Tcl_MethodIsType returns whether a method is of a particular type,
assigning the per-method clientData to the variable pointed to by
clientDataPtr if (that is non-NULL) if the type is matched.
METHOD CREATION
Methods are created by Tcl_NewMethod and Tcl_NewInstanceMethod, which
create a method attached to a class or an object respectively. In both
cases, the nameObj argument gives the name of the method to create, the
isPublic argument states whether the method should be exported ini‐
tially, the methodTypePtr argument describes the implementation of the
method (see the METHOD TYPES section below) and the clientData argument
gives some implementation-specific data that is passed on to the imple‐
mentation of the method when it is called.
When the nameObj argument to Tcl_NewMethod is NULL, an unnamed method
is created, which is used for constructors and destructors. Construc‐
tors should be installed into their class using the Tcl_ClassSetCon‐
structor function, and destructors (which must not require any argu‐
ments) should be installed into their class using the Tcl_ClassSetDe‐
structor function. Unnamed methods should not be used for any other
purpose, and named methods should not be used as either constructors or
destructors. Also note that a NULL methodTypePtr is used to provide
internal signaling, and should not be used in client code.
METHOD CALL CONTEXTS
When a method is called, a method-call context reference is passed in
as one of the arguments to the implementation function. This context
can be inspected to provide information about the caller, but should
not be retained beyond the moment when the method call terminates.
The method that is being called can be retrieved from the context by
using Tcl_ObjectContextMethod, and the object that caused the method to
be invoked can be retrieved with Tcl_ObjectContextObject. The number of
arguments that are to be skipped (e.g. the object name and method name
in a normal method call) is read with Tcl_ObjectContextSkippedArgs, and
the context can also report whether it is working as a filter for
another method through Tcl_ObjectContextIsFiltering.
During the execution of a method, the method implementation may choose
to invoke the stages of the method call chain that come after the cur‐
rent method implementation. This (the core of the next command) is done
using Tcl_ObjectContextInvokeNext. Note that this function does not
manipulate the call-frame stack, unlike the next command; if the method
implementation has pushed one or more extra frames on the stack as part
of its implementation, it is also responsible for temporarily popping
those frames from the stack while the Tcl_ObjectContextInvokeNext func‐
tion is executing. Note also that the method-call context is never
deleted during the execution of this function.
METHOD TYPES
The types of methods are described by a pointer to a Tcl_MethodType
structure, which is defined as:
typedef struct {
int version;
const char *name;
Tcl_MethodCallProc *callProc;
Tcl_MethodDeleteProc *deleteProc;
Tcl_CloneProc *cloneProc;
} Tcl_MethodType;
The version field allows for future expansion of the structure, and
should always be declared equal to TCL_OO_METHOD_VERSION_CURRENT. The
name field provides a human-readable name for the type, and is the
value that is exposed via the info class methodtype and info object
methodtype Tcl commands.
The callProc field gives a function that is called when the method is
invoked; it must never be NULL.
The deleteProc field gives a function that is used to delete a particu‐
lar method, and is called when the method is replaced or removed; if
the field is NULL, it is assumed that the method's clientData needs no
special action to delete.
The cloneProc field is either a function that is used to copy a
method's clientData (as part of Tcl_CopyObjectInstance) or NULL to
indicate that the clientData can just be copied directly.
TCL_METHODCALLPROC FUNCTION SIGNATURE
Functions matching this signature are called when the method is
invoked.
typedef int Tcl_MethodCallProc(
ClientData clientData,
Tcl_Interp *interp,
Tcl_ObjectContext objectContext,
int objc,
Tcl_Obj *const *objv);
The clientData argument to a Tcl_MethodCallProc is the value that was
given when the method was created, the interp is a place in which to
execute scripts and access variables as well as being where to put the
result of the method, and the objc and objv fields give the parameter
objects to the method. The calling context of the method can be discov‐
ered through the objectContext argument, and the return value from a
Tcl_MethodCallProc is any Tcl return code (e.g. TCL_OK, TCL_ERROR).
TCL_METHODDELETEPROC FUNCTION SIGNATURE
Functions matching this signature are used when a method is deleted,
whether through a new method being created or because the object or
class is deleted.
typedef void Tcl_MethodDeleteProc(
ClientData clientData);
The clientData argument to a Tcl_MethodDeleteProc will be the same as
the value passed to the clientData argument to Tcl_NewMethod or
Tcl_NewInstanceMethod when the method was created.
TCL_CLONEPROC FUNCTION SIGNATURE
Functions matching this signature are used to copy a method when the
object or class is copied using Tcl_CopyObjectInstance (or oo::copy).
typedef int Tcl_CloneProc(
Tcl_Interp *interp,
ClientData oldClientData,
ClientData *newClientDataPtr);
The interp argument gives a place to write an error message when the
attempt to clone the object is to fail, in which case the clone proce‐
dure must also return TCL_ERROR; it should return TCL_OK otherwise.
The oldClientData field to a Tcl_CloneProc gives the value from the
method being copied from, and the newClientDataPtr field will point to
a variable in which to write the value for the method being copied to.
SEE ALSOClass(3), oo::class(n), oo::define(n), oo::object(n)KEYWORDS
constructor, method, object
TclOO 0.1 Tcl_Method(3)
