1   // Copyright 2006, 2007, 2008 The Apache Software Foundation
    2   //
    3   // Licensed under the Apache License, Version 2.0 (the "License");
    4   // you may not use this file except in compliance with the License.
    5   // You may obtain a copy of the License at
    6   //
    7   //     http://www.apache.org/licenses/LICENSE-2.0
    8   //
    9   // Unless required by applicable law or agreed to in writing, software
   10   // distributed under the License is distributed on an "AS IS" BASIS,
   11   // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   12   // See the License for the specific language governing permissions and
   13   // limitations under the License.
   14   
   15   package org.apache.tapestry5;
   16   
   17   /**
   18    * Defines a field within a form.  Fields have a <a href="http://www.w3.org/TR/html4/interact/forms.html#control-name">control
   19    * name</a> that is used when rendering and, later, when the form is submitted, to identify the query parameter.
   20    * <p/>
   21    * Timing is important, as components may render multiple times, due to looping and other factors. Generally, a
   22    * component's {@link #getControlName()} will only be accurate after it has rendered.  In some cases, when generating
   23    * JavaScript for example, it is necessary to {@linkplain org.apache.tapestry5.services.Heartbeat#defer(Runnable) wait
   24    * until the end of the current Heartbeat} to ensure that all components have had thier chance to render.
   25    */
   26   public interface Field extends ClientElement
   27   {
   28       /**
   29        * Returns the value used as the name attribute of the rendered element. This value will be unique within an
   30        * enclosing form, even if the same component renders multiple times.
   31        *
   32        * @see org.apache.tapestry5.services.FormSupport#allocateControlName(String)
   33        */
   34       String getControlName();
   35   
   36       /**
   37        * Returns a user presentable (localized) label for the field, which may be used inside &lt;label&gt; elements on
   38        * the client, and inside client or server-side validation error messages.
   39        *
   40        * @return the label
   41        * @see org.apache.tapestry5.corelib.components.Label
   42        */
   43       String getLabel();
   44   
   45       /**
   46        * Returns true if the field is disabled; A disabled field will render a disabled attribute so that it is
   47        * non-responsive on the client (at least, until its disabled status is changed on the client using JavaScript). A
   48        * disabled field will ignore any value passed up in a form submit request. Care must be taken if the disabled
   49        * status of a field can change between the time the field is rendered and the time the enclosing form is
   50        * submitted.
   51        */
   52       boolean isDisabled();
   53   
   54       /**
   55        * Returns true if this field required (as per {@link org.apache.tapestry5.FieldValidator#isRequired()}).
   56        *
   57        * @return true if a non-blank value is required for the field
   58        */
   59       boolean isRequired();
   60   }