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Programming Social Applications by Jonathan LeBlanc

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Other Special Tags

In addition to the special tags we have already seen, os:Repeat and os:If, OpenSocial templates define a couple of reserved tags to enable developers to display data objects that are richer than simple strings. These special tags are os:Html and os:Render.

os:Html

When rendering data within escaped expressions or loops (i.e., not os:Repeat or os:If blocks), developers run into the issue that because all data is displayed as strings, they’re prevented from using a lot of rich data sets. When you’re using third-party data sources that are not necessarily trusted, this practice is a good option for sanitizing content. When a part of the source data is trusted, however, we need a means of rendering that data with the markup intact. This is where the os:Html tag comes in handy.

os:Html provides a means for a developer to render a block of data without having it automatically escaped and displayed as a string. The markup is rendered intact and applied to the template.

You use os:Html through the code attribute of the tag. Any data values within the code attribute are evaluated as a string and then rendered as HTML. For instance, if you have an object containing the viewer’s friends, and in that object you also have a name and a badge that contains HTML, you can easily render the badge HTML using the os:Html tag as follows:

<div repeat="${Top.ViewerFriends}">
   Name: ${Cur.name}<br />
   Badge:<br />
   <os:Html code="${Cur.badge}" />
</div>

Once rendered, name will be displayed as ...

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