Radio Buttons

Radio Buttons


	Radio buttons aren't really buttons, but appear as small circles that a user can "click" to activate a particular selection. Radio buttons differ from checkboxes in that only one selection can be active at a time. Whenever one of the radio buttons in a group is selected, all the others are automatically unselected.

	The term "radio button" refers to the pushbutton action commonly used in old car radios, where depression of one button would release all the other buttons.

	Radio buttons are represented by the htmlInputRadio class. A radio button can be initially checked or unchecked using the Check() method. The IsChecked() method allows you to test the state of an object in memory.

	Each radio button object is identified by a unique name, specified in the constructor or the Name() method. Typically, radio buttons are arranged as groups on a form allowing a user to select one of the options. The htmlInputRadioGroup class is used to assemble radio button objects sharing common attributes such as name and alignment.

	If htmlInputRadio is used independently of htmlInputRadioGroup, you must specify a name for the control to identify it on a form. Otherwise, you can leave the name argument of the constructor as an empty ("") string and the object will assume the name of the group to which it belongs.

	htmlInputRadio objects are added to forms and htmlInputRadioGroup objects using the << insertion operator or the Add() method.

	The descriptive text displayed beside a radio button is called it's "label", and is specified using the Label() method or a constructor argument. Labels may be aligned to the left or right of a radio button, and groups of radio buttons may be arranged horizontally or vertically.

	Do not confuse the value of a radio button object with it's label. The value of a radio button is a non-display string that's sent to the server when the form is submitted. For example, in a group of radio buttons representing a list of countries, the labels would be the names of the nations (e.g., "United State", "Mexico", etc.) while the values might be ordinal numbers or abbreviations. When a form containing a radio button group is submitted to a server, the value of the one selected radio button is included in the name/value pair list for the form.

Example

#include <stdio.h>

#include <stdlib.h>

#include <dcmicro/htmlpp/htmlpp.h>

int main( void )

{

   htmlCgi   server ;

   htmlPage  page( "html++ example application" ) ;

   //  Create a group to store the radio button

   //  objects. Each object with use the name

   //  "country" and will be right aligned (i.e.,

   //  the text labels will be to the right of the

   //  buttons).

   htmlInputRadioGroup group( "country" ) ;

   group.Align( align_right ) ;

   //  The first radio button will be checked.

   group << htmlInputRadio( "",

                  "america",

                  "United States of America",

                  STATE_CHECKED ) ;

   group << htmlInputRadio( "",

                  "argentina",

                  "Argentina" ) ;

   group << htmlInputRadio( "",

                  "mexico",

                  "Mexico" ) ;

   group << htmlInputRadio( "",

                  "uk",

                  "United Kingdom" ) ;

   //  Create a form, using a script for

   //  the submit action.

   htmlForm form( "/cgi-bin/script" ) ;

   //  Insert the radio button group and a

   //  submit button into the form.

   form << group

        << htmlBreak()

        << htmlInputSubmit() ;

   //  Insert the form into the page, then

   //  output the page.

   page << form ;

   server << page ;

   return 0 ;

}

Program Output

<HTML>

<HEAD>

<TITLE>html++ example application</TITLE>

</HEAD>

<BODY>

<FORM ACTION="/cgi-bin/script" METHOD="POST">

<INPUT TYPE="RADIO" VALUE="america" NAME="country" CHECKED>United States of America<BR>

<INPUT TYPE="RADIO" VALUE="argentina" NAME="country">Argentina<BR>

<INPUT TYPE="RADIO" VALUE="mexico" NAME="country">Mexico<BR>

<INPUT TYPE="RADIO" VALUE="uk" NAME="country">United Kingdom<BR>

<BR>

<INPUT TYPE="SUBMIT"></FORM>

</BODY>

</HTML>

©1998 DC Micro Development. All rights reserved.
No portion of this document may be c opied or reproduced without expressed written consent.
html++ is a trademark of DC Micro Development.


	#include <stdio.h>
	#include <stdlib.h>
	#include <dcmicro/htmlpp/htmlpp.h>

	int main( void )
	{
	htmlCgi server ;
	htmlPage page( "html++ example application" ) ;

	// Create a group to store the radio button
	// objects. Each object with use the name
	// "country" and will be right aligned (i.e.,
	// the text labels will be to the right of the
	// buttons).
	htmlInputRadioGroup group( "country" ) ;
	group.Align( align_right ) ;

	// The first radio button will be checked.
	group << htmlInputRadio( "",
	"america",
	"United States of America",
	STATE_CHECKED ) ;

	group << htmlInputRadio( "",
	"argentina",
	"Argentina" ) ;

	group << htmlInputRadio( "",
	"mexico",
	"Mexico" ) ;

	group << htmlInputRadio( "",
	"uk",
	"United Kingdom" ) ;

	// Create a form, using a script for
	// the submit action.
	htmlForm form( "/cgi-bin/script" ) ;

	// Insert the radio button group and a
	// submit button into the form.
	form << group
	<< htmlBreak()
	<< htmlInputSubmit() ;

	// Insert the form into the page, then
	// output the page.
	page << form ;

	server << page ;
	return 0 ;
	}


	<HTML>
	<HEAD>
	<TITLE>html++ example application</TITLE>
	</HEAD>
	<BODY>
	<FORM ACTION="/cgi-bin/script" METHOD="POST">
	<INPUT TYPE="RADIO" VALUE="america" NAME="country" CHECKED>United States of America<BR>
	<INPUT TYPE="RADIO" VALUE="argentina" NAME="country">Argentina<BR>
	<INPUT TYPE="RADIO" VALUE="mexico" NAME="country">Mexico<BR>
	<INPUT TYPE="RADIO" VALUE="uk" NAME="country">United Kingdom<BR>
	<BR>
	<INPUT TYPE="SUBMIT"></FORM>
	</BODY>
	</HTML>