Class representing ARIA state/property attribute. Contains methods for setting, getting, removing ARIA attributes for an HTML {@link com.google.gwt.dom.client.Element}.

For more details about ARIA states and properties check the W3C ARIA documentation Supported States and Properties .

@param <T> The attribute value type

abstract class Attribute<T> {

 final String name;
 String defaultValue;

 /**
  * Constructs a state/property ARIA attribute with name {@code name} and {@code defaultValue}.
  *
  * @param name State/Property name
  * @param defaultValue Default values
  */
 Attribute(this.name, [String defaultValue = null]) {
   assert (name != null); // : "Name cannot be null";
   this.defaultValue = defaultValue;
 }

 /**
  * Gets the HTML attribute value for the attribute with name {@code name} for element
  * {@code element}
  *
  * @param element HTM element
  * @return The attribute value for {@code element}
  */
 String get(dart_html.Element element) {
   assert (element != null); // : "Element cannot be null.";
   return element.attributes["name"];
 }

 /**
  * Gets the property/state name
  *
  * @return The attribute name
  */
 String getName() {
   return name;
 }

 /**
  * Removes the state/property attribute for element {@code element}.
  *
  * @param element HTM element
  */
 void remove(dart_html.Element element) {
   assert (element != null); // : "Element cannot be null.";
   element.attributes.remove(name);
 }

 /**
  * Sets the state/property {@code value} for the HTML element {@code element}.
  *
  * @param element HTML element
  * @param values Attribute value
  */
 void set(dart_html.Element element, T values) {
   assert (element != null); // : "Element cannot be null.";
   //assert (values.length > 0);
   element.attributes[name] = _getAriaValue(values);
 }

 /**
  * Sets the state/property value to the defaultValue if not null. If a list of default values is
  * set, every default value is converted to string and the string values are concatenated in a
  * string token list. There is an assertion checking whether the default is null. Note that the
  * asserts are enabled during development and testing but they will be stripped in production
  * mode.
  *
  * @param element HTML element
  */
 void setDefault(dart_html.Element element) {
   assert (element != null); // : "Element cannot be null.";
   assert (defaultValue != null && !defaultValue.isEmpty); // : "Default value cannot be null.";
   element.attributes[name] = defaultValue;
 }

 String getSingleValue(T value);

 String _getAriaValue(T value) {
   if (value is Iterable) {
     StringBuffer buf = new StringBuffer();
     for (T item in value) {
       buf.write(getSingleValue(item));
       buf.write(" ");
     }
     return buf.toString().trim();
   } else {
     return getSingleValue(value);
   }
//    if (value.length == 1) {
//      return getSingleValue(value[0]);
//    } else {
//      StringBuffer buf = new StringBuffer();
//      for (T item in value) {
//        buf.add(getSingleValue(item)).add(" ");
//      }
//      return buf.toString().trim();
//    }
 }
}