WideStudio Programming Guide	WideStudio Index Table of contents

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How to access to the GUI instances

During the event procedures, access to the instances is the most fundamental. So I will explain various ways of accessing the instance in this section.

• Accessing of the instance by the parameter of the event procedure
  
  In the event procedure which the instance has, we use the parameter of the procedure to access the instance,
  
  
• Accessing of the instance by using the instance management
  
  We use the instance management to access the instance except it which the event procedure is set.
  
  
• Accessing of the global instance directly
  
  You can use the global instance to access directly. it is easy to access and is good performance, but it makes the possibility of porting worse.

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Accessing of the instance by the parameter of the event procedure

open Swig
open Mwtlib
let event_procedure obj =
  (* accessing the instance.*)
  obj -> setProperty ("labelString","HELLO WORLD");
  ()
let _ = Callback.register "event_procedure" event_procedure

the pointer: obj is the instance which is the client of the event procedure that fired. the type is WSCbase, so you can access the method of WSCbase, but you must cast the pointer by the method:cast() to access the other subclass: see the chapter of casting sub class.

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Accessing of the instance by using the instance management

The instance management returns the instance by name.

The instance management class	The instance acquisition method
WSCbaseList	WSCbaseList _WSGIappObjectList '()

To access of the instance as follows:

open Swig
open Mwtlib

let event_procedure obj =
  (* Acquisition of the instance(1) *)
  let instance = _WSGIappObjectList '() -> getInstance (
                  "WSCvlabel",   (* Seek from the instance of WSCvlabel *)
                  "newvlab_001") (* the instance name is newvlab_001 *)
  in 
  instance -> setProperty ( "labelString", "HELLO WORLD");

  (* Acquisition of the instance(2) *)
  let instance2 = _WSGIappObjectList '() -> getInstance (
                  "WSCbase",     (* Seek from all the instances. *)
                  "newvlab_002") (* the instance name is newvlab_002 *)
  in 
  instance2 -> setProperty ( "labelString", "HELLO WORLD");
  ()
let _ = Callback.register "event_procedure" event_procedure

The variable: obj is the sought instance by the specified class name and the specified instance name. If you do not want to specify the class name, you can pass "WSCbase", it seeks from all the instances.

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Accessing of the global instance directly

Make the instance global,you can access it directly. See the chapter [Setting of global instance] of Application Builder User's Guide to make it global.

...
let event_procedure obj =
  (* Access the instance of WSCvlabel*: newvlab_001 *)
  !newvlab_001 -> setProperty ("labelString","HELLO WORLD");
let _ = Callback.register "event_procedure" event_procedure