[Tapestry Wiki] Update of "Tapestry5HowToAddBindingPrefixCycle" by DavorHrg

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The following page has been changed by DavorHrg:
http://wiki.apache.org/tapestry/Tapestry5HowToAddBindingPrefixCycle

New page:
this is another example like : Tapestry5HowToAddBindingPrefix

This binding prefix will return different value for each call,
and we will use it for zebra effect on grid or any other loop.

First let's see usage example:
{{{
<t:grid ....  rowClass="cycle:line1,line2">
...
</t:grid>
}}}
that is it, no need for counter, and counter % 2 and stuff..


To make it wor you have to tell tapestry about the "cycle:" binding prefix. So, 
add following to your module:
{{{#!java
    public static void contributeBindingSource(
            MappedConfiguration<String, BindingFactory> configuration,
            BindingSource bindingSource
            )
    {
        configuration.add("cycle",new CycleBindingFactory(bindingSource));
    }    
}}}

And you'll need the implementation:
{{{#!java
import java.util.ArrayList;
import java.util.List;

import org.apache.tapestry.Binding;
import org.apache.tapestry.ComponentResources;
import org.apache.tapestry.TapestryConstants;
import org.apache.tapestry.ioc.Location;
import org.apache.tapestry.services.BindingFactory;
import org.apache.tapestry.services.BindingSource;

/**
 * Implementation of the cycle: binding prefix -- we parse list of bindings
 * and generate delegate bindings for each element<br>
 * default binding is literal, other bindings can be used by specifying 
prefix.<br>
 * example: "cycle:prop:name,prop:lastName,sth,sth else"
 */
public class CycleBindingFactory implements BindingFactory {
    private final BindingSource _bindingSource;

    public CycleBindingFactory(BindingSource source){
        this._bindingSource = source;
    }
    
    public Binding newBinding(String description, ComponentResources container, 
ComponentResources component,
            String expression, Location location)
    {
        List<Binding> delegates = new ArrayList<Binding>();
        String[] bindingNames = expression.split(",");

        for (String bindingName : bindingNames){
            String defaultBinding = TapestryConstants.LITERAL_BINDING_PREFIX;

            Binding binding = _bindingSource.newBinding(description, container, 
component, defaultBinding, bindingName, location);
            delegates.add(binding);
        }
        
        CycleBinding cycleBinding = new CycleBinding(delegates);
        container.addPageLifecycleListener(cycleBinding);
            
        return cycleBinding;
    }
}
}}}

and this also:
{{{#!java

import java.util.List;

import org.apache.tapestry.Binding;
import org.apache.tapestry.internal.bindings.AbstractBinding;
import org.apache.tapestry.runtime.PageLifecycleListener;

public class CycleBinding extends AbstractBinding implements 
PageLifecycleListener{
    private final List<Binding> delegates;
    private int index = 0;

    public CycleBinding(List<Binding> delegates) {
        this.delegates = delegates;
    }

    public Object get() {
        Object ret = delegates.get(index).get();
        index ++; 
        if(index>=delegates.size()) index = 0;
        return ret;
    }
    
    @Override
    public boolean isInvariant() {
        return false;
    }
    
    @Override
    public Class<Object> getBindingType() {
        return Object.class;
    }


    public void containingPageDidDetach() {
        index=0;
    }

    public void containingPageDidAttach() {/*not interested*/}
    
    public void containingPageDidLoad() {/*not interested*/}
}

}}}

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