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Itcl_RegisterC(3) [incr Tcl] Library Procedures Itcl_RegisterC(3) NAME Itcl_RegisterC, Itcl_RegisterObjC, Itcl_FindC - Associate a symbolic name with a C procedure. SYNOPSIS #include <itcl.h> int Itcl_RegisterC(interp, cmdName, argProc, clientData, deleteProc) int Itcl_RegisterObjC(interp, cmdName, objProc, clientData, deleteProc) int Itcl_FindC(interp, cmdName, argProcPtr, objProcPtr, cDataPtr) ARGUMENTS Interpreter in which to create new command. Name of command. Imple- mentation of new command: argProc will be called whenever The Tcl_Cmd- Proc * to receive the pointer. Implementation of the new command: ob- jProc will be called whenever The Tcl_ObjCmdProc * to receive the pointer. Arbitrary one-word value to pass to proc and deleteProc. The ClientData to receive the pointer. Procedure to call before cmdName is deleted from the interpreter; allows for command-specific cleanup. If NULL, then no procedure is called before the command is deleted. DESCRIPTION Used to associate a symbolic name with an (argc,argv) C procedure that handles a Tcl command. Procedures that are registered in this manner can be referenced in the body of an [incr Tcl] class definition to specify C procedures to acting as methods/procs. Usually invoked in an initialization routine for an extension, called out in Tcl_AppInit() at the start of an application. Each symbolic procedure can have an arbitrary client data value associ- ated with it. This value is passed into the command handler whenever it is invoked. A symbolic procedure name can be used only once for a given style (arg/obj) handler. If the name is defined with an arg-style handler, it can be redefined with an obj-style handler; or if the name is de- fined with an obj-style handler, it can be redefined with an arg-style handler. In either case, any previous client data is discarded and the new client data is remembered. However, if a name is redefined to a different handler of the same style, this procedure returns an error. Returns TCL_OK on success, or TCL_ERROR (along with an error message in interp->result) if anything goes wrong. C procedures can be integrated into an [incr Tcl] class definition to implement methods, procs, and the "config" code for public variables. Any body that starts with "@" is treated as the symbolic name for a C procedure. Symbolic names are established by registering procedures via Itcl_Reg- isterC(). This is usually done in the Tcl_AppInit() procedure, which is automatically called when the interpreter starts up. In the follow- ing example, the procedure My_FooCmd() is registered with the symbolic name "foo". This procedure can be referenced in the body command as "@foo". int Tcl_AppInit(interp) Tcl_Interp *interp; /* Interpreter for application. */ { if (Itcl_Init(interp) == TCL_ERROR) { return TCL_ERROR; } if (Itcl_RegisterC(interp, "foo", My_FooCmd) != TCL_OK) { return TCL_ERROR; } } C procedures are implemented just like ordinary Tcl commands. See the CrtCommand man page for details. Within the procedure, class data members can be accessed like ordinary variables using Tcl_Set- Var(), Tcl_GetVar(), Tcl_TraceVar(), etc. Class methods and procs can be executed like ordinary commands using Tcl_Eval(). [incr Tcl] makes this possible by automatically setting up the context before executing the C procedure. This scheme provides a natural migration path for code development. Classes can be developed quickly using Tcl code to implement the bod- ies. An entire application can be built and tested. When necessary, individual bodies can be implemented with C code to improve perfor- mance. See the Archetype class in [incr Tk] for an example of how this C link- ing method is used. SEE ALSO Tcl_CreateCommand, Tcl_CreateObjCommand KEYWORDS class, object itcl 3.0 Itcl_RegisterC(3)
NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | SEE ALSO | KEYWORDS
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