package net.sf.tapestry.form;

/**
 *  Used by a {@link PropertySelection} to provide labels for options.
 *
 *  <p>The component requires three different representations
 *  of each option:
 *  <ul>
 *  <li>The option value, a Java object that will eventually be assigned to
 *  a property
 *  <li>The label, a String which is incorprated into the HTML to identify the
 *  option to the user
 *  <li>The value, a String which is used to represent the option as the value
 *  of the &lt;option&gt; or &lt;input type=radio&gt; generated by the
 *  {@link PropertySelection}.
 *  </ul>
 *
 *  <p>The option is usually either an {@link net.sf.tapestry.util.Enum} 
 *  (see {@link EnumPropertySelectionModel})
 *  or some kind of business object.  The label is often a property of the
 *  option object (for example, for a list of customers, it could be the customer name).
 *
 *  <p>It should be easy to convert between the value and the option.  It may simply
 *  be an index into an array.  For business objects, it is often the primary key
 *  of the object, expressed as a String.
 *
 *  @version $Id: IPropertySelectionModel.java,v 1.4 2002/11/27 17:58:47 hship Exp $
 *  @author Howard Lewis Ship
 *
 **/

public interface IPropertySelectionModel
{
    /**
     *  Returns the number of possible options.
     *
     **/

    public int getOptionCount();

    /**
     *  Returns one possible option.
     *
     **/

    public Object getOption(int index);

    /**
     *  Returns the label for an option.  It is the responsibility of the
     *  adaptor to make this value localized.
     *
     **/

    public String getLabel(int index);

    /**
     *  Returns a String used to represent the option in the HTML (as the
     *  value of an &lt;option&gt; or &lt;input type=radio&gt;.
     *
     **/

    public String getValue(int index);

    /**
     *  Returns the option corresponding to a value.  This is used when
     *  interpreting submitted form parameters.
     *
     **/

    public Object translateValue(String value);
}