Guide_English

Complementary guide rapidq on components/objects definition.

USE OF API FUNCTIONS WINDOW IN AN OBJECT TYPE.

PARENT PROPERTY OF VISIBLE COMPONENTS.

1) REDEFINITION OF INHERITED EVENT.

If an inherited event is redefined within a new object, its use requires the call of the event with the key word inherit in the routine allotted has this event as indicated in the documentation of origin. In order to avoid the use of this key word, which can be forgotten at the time of the writing of a program, one can create an event additional having the same function as that which is redefined but with an other name and called by the redefined event.
So the actions added in the redefined event will be carried out without having has to add the call of the event with the allotted key word inherit in the routine has this one.
However, it is not possible to mask the event redefined with the key word Private in the structure of the object for the user.
In the example below, the OnClick event inherited object QBUTTON is redefined with an action on its Caption property with a call of routine associated with the new On_Click event created in the object.

EXAMPLE:
$TYPECHECK ON
$Include "Rapidq.inc"

Declare Sub routine1
Declare Sub event_click

Type button extends QBUTTON
On_Click as EVENT(event_click)

          EVENT OnClick
            button.caption="check"
            if button.On_Click<>0 then CALLFUNC button.On_Click
          END EVENT
        End type

        CREATE Form AS QFORM
          Caption="Form1"
          Width=320
          Height=240
          Center
          CREATE Button1 AS button
           Caption="Button1"
           Left=34
           Top=41
           On_Click=routine1
         END CREATE
     END CREATE

Form.ShowModal

     sub routine1
      form.Caption = "check"
     end sub

2) USE OF API FUNCTIONS WINDOW IN AN OBJECT TYPE.

An object using of the API functions to call an external file little comprising the declaration of all the API functions but that would increase the size of the program compiled with the final one.

The declaration of API functions can be included in the file of the component object, but as several object can use the same API functions , there
are two way of proceeding in order to avoid a multiple declaration for the same function:

a) To use the directives of compilation:

    $IFNDEF API_1
      $DEFINE API_1
      Declare Function GetDC Lib "user32" Alias "GetDC" (ByVal hwnd As Long) As Long
    $ENDIF

b) To use names of function different for the same API function:

Declare Function GetDC_ObjectName Lib "user32" Alias "GetDC" (ByVal hwnd As Long) As Long

the example above uses the name of the object in extension of the name of the function.
The constants necessary to the API functions can be declared same manner.

3) PARENT PROPERTY OF VISIBLE COMPONENTS.

A new object inheriting a standard object does not need to have its parent property redefined.
On the other hand if one adds components visible as a new field of the object, it is necessary to carry out the assignment of the parent
properties of each one in the routine constructor or a method.

EXAMPLE:

   Type a extends QPanel
     bt as qbutton
     img as qimage

     constructor
       bt.parent=a
       img.parent=a
     end constructor
   end type

If a new object is created without heritage and using API functions to obtain a visible component, a field parent must be defined in this one.
This field parent must be of Long type or Integer and can be defined like property using routines PROPERTY.
This object will be able to be imbricated in a structure CREATE has condition of carrying out the assignment of the property parent by the handle of the parent object.

EXAMPLE:
Type a extends QObject
Parent as integer PROPERTY SET SetParent

    PROPERTY SET SetParent(parent as integer)
      a.Parent=parent
      'use handle parent for API function
    END PROPERTY
   end type

   CREATE Form as QFORM
     width=200
     height=100
     CREATE obj as a
       parent=form.handle
     END CREATE
   END CREATE

Form.ShowModal

Another method of definition exists but does not allow the overlap with CREATE, it consists has to pass the parent object in parameter at the time of the declaration of a variable of personalized the object type.
The only problem being which one can have only of the objects of a single type identified by the parameter of the object type.
In the example below the property parent is initialized in the routine constructor object, so it is not necessary to affect the property parent in the program since the Obj variable is declared with the Form variable passed in parameter.

EXAMPLE:

Type a<QFORM> extends QObject
parent as long

     constructor
       parent=QFORM.handle
     end constructor
   end type

   CREATE Form as QFORM
     width=200
     height=100
   END CREATE

dim obj as a<Form>

Form.ShowModal

4) PROTECTION OF FIELDS OBJECT

If the fields of an object are accessible in reading as in writing for the user, it is possible to limit their access in reading only by defining them in property.
In the example below, the field parent is defined in property and can be used in reading in a program.
When the user wants used the property in writing, the field parent is not modified since its assignment is not carried out in routine PROPERTY and only the methods of the object can modify the state of the field parent.
One can also put routine PROPERTY as a member deprived by adding PRIVATE: before this one in order to have an error of so tentative compilation of writing of the field parent.

EXAMPLE:
Type a extends QObject
Parent as integer PROPERTY SET SetParent

   PRIVATE:
     PROPERTY SET SetParent(parent as integer)
     END PROPERTY
   end type

5) LIMITATIONS KNOWN.

a) the heritage of components personalized is not supported.

b) Some method redefined of an inherited object require an addition of parameter in order to avoid an error of compilation.
this is the case for the Show methods and ShowModal of an object QFORM as the example shows it below.

EXAMPLE:

Type b extends qform

      sub Showmodal(title as string)
        b.caption =title
        Super.Showmodal
      end sub
    end type

    CREATE Form AS b
      Caption = "Rapid-Q Code Viewer"
      Width = 234
      Height = 251
      Center
      OnClick=show
    END CREATE

Form.ShowModal ("Check")

c) If one uses variables local of the same name in the methods of a personalized object, the object cannot be declared in local variable of a routine but only into total of the program.
This can be solved by having different variables local of name in the methods of an object.
In the same way, two objects cannot have the same name of variables local in their methods if they are declared in local variable of a routine.
The solution has this say operation will be to declare these variables in fields private of the object and not to have any variables local in the methods of this one.

d) The components personalized cannot have passed in parameters of a routine.