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. Implementa- tion of new command: argProc will be called whenever The Tcl_CmdProc * to receive the pointer. Implementation of the new command: objProc 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 inter- preter; 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 han- dles 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 pro- cedures 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 associated with it. This value is passed into the command handler whenever it is in- voked. 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 rede- fined with an obj-style handler; or if the name is defined 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 re- membered. 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 in- terp->result) if anything goes wrong. C procedures can be integrated into an [incr Tcl] class definition to im- plement methods, procs, and the "config" code for public variables. Any body that starts with "@" is treated as the symbolic name for a C proce- dure. Symbolic names are established by registering procedures via Itcl_Regis- terC(). This is usually done in the Tcl_AppInit() procedure, which is au- tomatically called when the interpreter starts up. In the following exam- ple, 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 mem- bers can be accessed like ordinary variables using Tcl_SetVar(), Tcl_Get- Var(), Tcl_TraceVar(), etc. Class methods and procs can be executed like ordinary commands using Tcl_Eval(). [incr Tcl] makes this possible by au- tomatically 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 bodies. An entire application can be built and tested. When necessary, individual bodies can be implemented with C code to improve performance. See the Archetype class in [incr Tk] for an example of how this C linking method is used. SEE ALSO Tcl_CreateCommand, Tcl_CreateObjCommand KEYWORDS class, object itcl 3.0 Itcl_RegisterC(3)
Want to link to this manual page? Use this URL:
<https://man.FreeBSD.org/cgi/man.cgi?query=Itcl_RegisterC&sektion=3&manpath=FreeBSD+Ports+15.1.quarterly>