Dynamic Key Placeholders Revisited

A little over a year ago I did a post on Dynamic Key Placeholders, since then I have noticed there was some information lacking, such as what versions of Sitecore it works with, and how to get Placeholder Settings to work.

From my testing this should work in every version of Sitecore from 6.5 to 8.0, and likely will continue working in previous and future versions as well.

The Old Way  

By default when using dynamic key placeholders you can create placeholder settings for each index of the key.  Such as if the original key was Placeholder, you would need to create settings for Placeholder1, Placeholder2, etc… This can lead to a lot of work, and a cluttered collection of placeholder settings.

 

A New Way to Do It

An easier way would be to create an override of the GetAllowedRenderings processor to allow for an experience more like the original when creating placeholder settings.

A Quick Modification to the Original

In the original source for the dynamic key placeholders we need to make a simple modification.  In the part of the code that we set the key I have added the # symbol in there to allow us to split it apart far easier to create an override for Placeholder Settings.  You can use any symbol you want, but keep I will continue with this one for the rest of the post.

                // Count represents how many of the same container have already been added to the page

                if (renderings.Any())

                {

                    _dynamicKey = _key + "#" + renderings.Count();

                }

Our New Processor

The big changes though are in the addition of overriding the GetAllowedRenderings processor.  The change is not too complex as we are basically mirroring what Sitecore is already doing, but with the exception of overriding the placeholder key.

To override the key we want to split the key first into the segments by the / character and then for each segment we use the split on the # to remove our index from the dynamic key giving us the original key.

After that we want to try to get the placeholder item using our cleaned up key.  Of course if there is a device specified we should get the item in the context of that device.

If the Item exists we should get the list of renderings it supports.

    public class GetAllowedRenderings : Sitecore.Pipelines.GetPlaceholderRenderings.GetAllowedRenderings

    {

        /// <summary>

        /// This is a method based on the original Sitecore method to allow for dynamic placeholder keys

        /// </summary>

        /// <param name="args">The Placeholder Rendering Args (Device, Key, Database, etc...)</param>

        public new void Process(GetPlaceholderRenderingsArgs args)

        {

            Assert.IsNotNull((object)args, "args");

            //Remove the dynamic indexing from the key

            var key = string.Join("/", args.PlaceholderKey.Split('/').Select(i => i.Split('#')[0]));

            //Get the placeholder item, if there is a Device selected get it using that Device Context

            Item placeholderItem = null;

            if (ID.IsNullOrEmpty(args.DeviceId))

            {

                placeholderItem = Client.Page.GetPlaceholderItem(key, args.ContentDatabase, args.LayoutDefinition);

            }

            else

            {

                using (new DeviceSwitcher(args.DeviceId, args.ContentDatabase))

                {

                    placeholderItem = Client.Page.GetPlaceholderItem(key, args.ContentDatabase, args.LayoutDefinition);

                }

            }

           

            //If there was a placeholder item (Placeholder Settings) set the allowed renderings

            if (placeholderItem != null)

            {

                args.HasPlaceholderSettings = true;

                bool allowedControlsSpecified;

                args.PlaceholderRenderings = this.GetRenderings(placeholderItem, out allowedControlsSpecified);

                if (allowedControlsSpecified)

                    args.Options.ShowTree = false;

            }

        }

    }

Our Configuration Change

Finally we have the configuration file to enable this override, this is simply done by replacing the processor in the getPlaceholderRenderings pipeline.

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">

  <sitecore>

    <pipelines>

      <getPlaceholderRenderings>                              

        <processor patch:instead="*[@type='Sitecore.Pipelines.GetPlaceholderRenderings.GetAllowedRenderings, Sitecore.Kernel']" type="[Your Method], [Your Assembly] />

      </getPlaceholderRenderings>

    </pipelines>

  </sitecore>   

</configuration>

You can find the source from this post at https://github.com/musicman89/Sitecore-Dynamic-Key-Placeholders

Update (4/10/2015):

You can find a Shared Source Module created at the Sitecore Hackathon 2015 that incorporates this concept at https://marketplace.sitecore.net/en/Modules/Integrated_Dynamic_Placeholders.aspx by Jamie Stump and Mark Servais, do note that I had no involvement in the creation of this module.

Thank you Jamie Stump for pointing this out.