NAME¶
Tcl_ClassGetMetadata, Tcl_ClassSetMetadata, Tcl_CopyObjectInstance,
Tcl_GetClassAsObject, Tcl_GetObjectAsClass, Tcl_GetObjectCommand,
Tcl_GetObjectFromObj, Tcl_GetObjectName, Tcl_GetObjectNamespace,
Tcl_NewObjectInstance, Tcl_ObjectDeleted, Tcl_ObjectGetMetadata,
Tcl_ObjectGetMethodNameMapper, Tcl_ObjectSetMetadata,
Tcl_ObjectSetMethodNameMapper - manipulate objects and classes
SYNOPSIS¶
#include <tclOO.h>
Tcl_Object
Tcl_GetObjectFromObj(interp, objPtr)
Tcl_Object
Tcl_GetClassAsObject(class)
Tcl_Class
Tcl_GetObjectAsClass(object)
Tcl_Obj *
Tcl_GetObjectName(interp, object)
Tcl_Command
Tcl_GetObjectCommand(object)
Tcl_Namespace *
Tcl_GetObjectNamespace(object)
Tcl_Object
Tcl_NewObjectInstance(interp, class, name, nsName, objc, objv, skip)
Tcl_Object
Tcl_CopyObjectInstance(interp, object, name, nsName)
int
Tcl_ObjectDeleted(object)
ClientData
Tcl_ObjectGetMetadata(object, metaTypePtr)
Tcl_ObjectSetMetadata(object, metaTypePtr, metadata)
ClientData
Tcl_ClassGetMetadata(class, metaTypePtr)
Tcl_ClassSetMetadata(class, metaTypePtr, metadata)
Tcl_ObjectMapMethodNameProc
Tcl_ObjectGetMethodNameMapper(object)
Tcl_ObjectSetMethodNameMapper(object, methodNameMapper)
ARGUMENTS¶
- Tcl_Interp *interp (in/out)
- Interpreter providing the context for looking up or creating an object,
and into whose result error messages will be written on failure.
- Tcl_Obj *objPtr (in)
- The name of the object to look up.
- Tcl_Object object (in)
- Reference to the object to operate upon.
- Tcl_Class class (in)
- Reference to the class to operate upon.
- const char *name (in)
- The name of the object to create, or NULL if a new unused name is to be
automatically selected.
- const char *nsName (in)
- The name of the namespace to create for the object's private use, or NULL
if a new unused name is to be automatically selected.
- int objc (in)
- The number of elements in the objv array.
- Tcl_Obj *const *objv (in)
- The arguments to the command to create the instance of the class.
- int skip (in)
- The number of arguments at the start of the argument array, objv,
that are not arguments to any constructors.
- Tcl_ObjectMetadataType *metaTypePtr (in)
- The type of metadata being set with Tcl_ClassSetMetadata or
retrieved with Tcl_ClassGetMetadata.
- ClientData metadata (in)
- An item of metadata to attach to the class, or NULL to remove the metadata
associated with a particular metaTypePtr.
- Tcl_ObjectMapMethodNameProc methodNameMapper (in)
- A pointer to a function to call to adjust the mapping of objects and
method names to implementations, or NULL when no such mapping is required.
DESCRIPTION¶
Objects are typed entities that have a set of operations ("methods")
associated with them. Classes are objects that can manufacture objects. Each
class can be viewed as an object itself; the object view can be retrieved
using
Tcl_GetClassAsObject which always returns the object when applied
to a non-destroyed class, and an object can be viewed as a class with the aid
of the
Tcl_GetObjectAsClass (which either returns the class, or NULL if
the object is not a class). An object may be looked up using the
Tcl_GetObjectFromObj function, which either returns an object or NULL
(with an error message in the interpreter result) if the object cannot be
found. The correct way to look up a class by name is to look up the object
with that name, and then to use
Tcl_GetObjectAsClass.
Every object has its own command and namespace associated with it. The command
may be retrieved using the
Tcl_GetObjectCommand function, the name of
the object (and hence the name of the command) with
Tcl_GetObjectName,
and the namespace may be retrieved using the
Tcl_GetObjectNamespace
function. Note that the Tcl_Obj reference returned by
Tcl_GetObjectName
is a shared reference.
Instances of classes are created using
Tcl_NewObjectInstance, which
creates an object from any class (and which is internally called by both the
create and
new methods of the
oo::class class). It takes
parameters that optionally give the name of the object and namespace to
create, and which describe the arguments to pass to the class's constructor
(if any). The result of the function will be either a reference to the newly
created object, or NULL if the creation failed (when an error message will be
left in the interpreter result). In addition, objects may be copied by using
Tcl_CopyObjectInstance which creates a copy of an object without
running any constructors.
Every object and every class may have arbitrary amounts of metadata attached to
it, which the object or class attaches no meaning to beyond what is described
in a Tcl_ObjectMetadataType structure instance. Metadata to be attached is
described by the type of the metadata (given in the
metaTypePtr
argument) and an arbitrary pointer (the
metadata argument) that are
given to
Tcl_ObjectSetMetadata and
Tcl_ClassSetMetadata, and a
particular piece of metadata can be retrieved given its type using
Tcl_ObjectGetMetadata and
Tcl_ClassGetMetadata. If the
metadata parameter to either
Tcl_ObjectSetMetadata or
Tcl_ClassSetMetadata is NULL, the metadata is removed if it was
attached, and the results of
Tcl_ObjectGetMetadata and
Tcl_ClassGetMetadata are NULL if the given type of metadata was not
attached. It is not an error to request or remove a piece of metadata that was
not attached.
The contents of the Tcl_ObjectMetadataType structure are as follows:
typedef const struct {
int version;
const char * name;
Tcl_ObjectMetadataDeleteProc * deleteProc;
Tcl_CloneProc * cloneProc;
} Tcl_ObjectMetadataType;
The
version field allows for future expansion of the structure, and
should always be declared equal to TCL_OO_METADATA_VERSION_CURRENT. The
name field provides a human-readable name for the type, and is reserved
for debugging.
The
deleteProc field gives a function of type
Tcl_ObjectMetadataDeleteProc that is used to delete a particular piece of
metadata, and is called when the attached metadata is replaced or removed; the
field must not be NULL.
The
cloneProc field gives a function that is used to copy a piece of
metadata (used when a copy of an object is created using
Tcl_CopyObjectInstance); if NULL, the metadata will be just directly
copied.
Functions matching this signature are used to delete metadata associated with a
class or object.
typedef void Tcl_ObjectMetadataDeleteProc(
ClientData metadata);
The
metadata argument gives the address of the metadata to be deleted.
TCL_CLONEPROC FUNCTION SIGNATURE¶
Functions matching this signature are used to create copies of metadata
associated with a class or object.
typedef int Tcl_CloneProc(
Tcl_Interp * interp,
ClientData srcMetadata,
ClientData * dstMetadataPtr);
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 procedure must
also return TCL_ERROR; it should return TCL_OK otherwise. The
srcMetadata argument gives the address of the metadata to be cloned,
and the cloned metadata should be written into the variable pointed to by
dstMetadataPtr; a NULL should be written if the metadata is to not be
cloned but the overall object copy operation is still to succeed.
OBJECT METHOD NAME MAPPING¶
It is possible to control, on a per-object basis, what methods are invoked when
a particular method is invoked. Normally this is done by looking up the method
name in the object and then in the class hierarchy, but fine control of
exactly what the value used to perform the look up is afforded through the
ability to set a method name mapper callback via
Tcl_ObjectSetMethodNameMapper (and its introspection counterpart,
Tcl_ObjectGetMethodNameMapper, which returns the current mapper). The
current mapper (if any) is invoked immediately before looking up what chain of
method implementations is to be used.
TCL_OBJECTMAPMETHODNAMEPROC FUNCTION SIGNATURE¶
The
Tcl_ObjectMapMethodNameProc callback is defined as follows:
typedef int Tcl_ObjectMapMethodNameProc(
Tcl_Interp * interp,
Tcl_Object object,
Tcl_Class * startClsPtr,
Tcl_Obj * methodNameObj);
If the result is TCL_OK, the remapping is assumed to have been done. If the
result is TCL_ERROR, an error message will have been left in
interp and
the method call will fail. If the result is TCL_BREAK, the standard method
name lookup rules will be used; the behavior of other result codes is
currently undefined. The
object parameter says which object is being
processed. The
startClsPtr parameter points to a variable that contains
the first class to provide a definition in the method chain to process, or
NULL if the whole chain is to be processed (the argument itself is never
NULL); this variable may be updated by the callback. The
methodNameObj
parameter gives an unshared object containing the name of the method being
invoked, as provided by the user; this object may be updated by the callback.
SEE ALSO¶
Method(3tcl), oo::class(3tcl), oo::copy(3tcl), oo::define(3tcl),
oo::object(3tcl)
KEYWORDS¶
class, constructor, object