// Copyright 2004, 2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry.components;
import org.apache.hivemind.util.Defense;
import org.apache.tapestry.AbstractComponent;
import org.apache.tapestry.IComponent;
import org.apache.tapestry.IMarkupWriter;
import org.apache.tapestry.IRequestCycle;
/**
* Prevents its contents from being rendered until triggered by an {@link RenderBlock} component. [<a
* href="../../../../../ComponentReference/Block.html">Component Reference</a>]
* <p>
* Block and {@link RenderBlock} are used to build a certain class of complicated component that
* can't be assembled using the normal wrapping containment. Such a super component would have two
* or more sections that need to be supplied by the containing page (or component).
* <p>
* Using Blocks, the blocks can be provided as parameters to the super component.
* <p>
* The invoker property gives the components inside the block access to the component (typically an
* {@link RenderBlock}) that rendered the block. More often, the {@link #getParameter(String)}
* method is used to get parameters <em>of the invoking component</em>.
*
* @author Howard Lewis Ship
* @since 0.2.9
*/
public abstract class Block extends AbstractComponent
{
private IComponent _invoker;
/**
* Provides access to the invoking component's parameters.
*
* @since 4.0
*/
public Object getParameter(String name)
{
return _invoker.getBinding(name).getObject();
}
public void renderForComponent(IMarkupWriter writer, IRequestCycle cycle, IComponent invoker)
{
Defense.notNull(invoker, "invoker");
IComponent oldInvoker = _invoker;
try
{
_invoker = invoker;
renderBody(writer, cycle);
}
finally
{
_invoker = oldInvoker;
}
}
/**
* Does nothing; the idea of a Block is to defer the rendering of the body of the block until an
* {@link RenderBlock} forces it out.
*/
protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
{
// Nothing!
}
/**
* Returns the object which invoked this Block's
* {@link #renderForComponent(IMarkupWriter, IRequestCycle, IComponent)} method. This is often
* used to access the informal parameters of a {@link RenderBlock} component.
*
* @since 4.0
*/
public IComponent getInvoker()
{
return _invoker;
}
/**
* Used for testing only.
*
* @since 4.0
*/
void setInvoker(IComponent invoker)
{
_invoker = invoker;
}
}