Q131838: How OptionGroup Buttons Behave

Article: Q131838
Product(s): Microsoft FoxPro
Version(s): 
Operating System(s): 
Keyword(s): 
Last Modified: 25-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
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SUMMARY
=======

This article describes how OptionGroup buttons function.

MORE INFORMATION
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Determining Which Option Button Is Clicked in an Option Group
-------------------------------------------------------------

With FoxPro version 2.x, you could determine which radio button was clicked by
setting up a case structure to return the number of the clicked radio button.

In Visual FoxPro, radio buttons are called OptionGroup buttons, and in most
cases, you no longer need a case structure to determine which option was
clicked. Each OptionGroup button in the group can respond to a click event
independently.

Step-by-Step Example
--------------------

1. Create a new form in Visual FoxPro. Using the OptionGroup tool, place a set
  (two is the default) of OptionGroup buttons on the form.

2. Double-click the OptionGroup object to bring up the code editor, and click
  Option1 so that you can edit the code for the events associated with the
  option button. Select the Click procedure. In the code editing window, type:

     Wait window "option button 1"

3. On the Object menu, click Option2. Then select the Click procedure. In the
  code editing window, type:

     Wait window "option button 2"

4. Run the form, and click the different option buttons. You should see the
  different wait windows activate with the appropriate text for each button.

Calling Parent Code
-------------------

It is possible to encapsulate code even further by using the concept of an parent
object. Option buttons are part of an OptionGroup class, so the OptionGroup
object is called the parent or the container of the buttons. Messages can be
sent to a parent object by prefacing the method call with this.parent.

In the following example, a set of OptionGroup buttons send messages to the Click
method of the OptionGroup container (parent object):

1. Create a new form.

2. Place an OptionGroup object on the form, and change the button count property
  to 3.

3. In each option button's Click procedure, place this code:

     this.parent.click

4. Change the Caption and Name property of the three buttons to Red, Green, and
  Blue.

5. Place the following code in the Click procedure of the OptionGroup object
  itself:

     do case
     case this.value='red'
          thisform.backcolor=rgb(255,0,0)
     case this.value='green'
          thisform.backcolor=rgb(0,255,0)
     case this.value='blue'
          thisform.backcolor=rgb(0,255,0)
     endcase

6. Set the Value property of the OptionGroup object to "" (an empty string), so
  it is created (instantiated) with a character data type.

7. Run the form.

8. Click the different option buttons, and observe the behaviors.

The individual buttons call the parent object's Click procedure. The parent
object in this case is the OptionGroup container. This code checks the Value
property and determines, by using the case structure, which values to use when
setting the form's background color.

Calling Button Code from the Parent
-----------------------------------

To run a given button's code from the OptionGroup object, refer to the event for
that particular button. For example, the Click event of the OptionGroup object
could run Option1 button's code with this code:

     this.option1.click

This causes the code in the Click procedure of the Option1 button to run whenever
the user clicks the option group frame instead of an actual button. Of course,
the code in the Option1 Click procedure also runs when the user clicks the
Option1 button directly. But even if another button had the focus, and the user
clicks within the frame of the OptionGroup container, the code for the Option1
button is run.

Additional query words: VFoxWin

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300

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