Posts Tagged “fsharp”

Thursday, November 24, 2022
  Fragment Rendering in Giraffe View Engine

A few months back, Carson Gross, author of the outstanding htmx library, wrote an essay entitled “Template Fragments”; if you are unfamiliar with the concept, read that first.

The goal is to allow an application to render a partial view without defining that partial view as its own template, in its own file. A common pattern in hypermedia-driven applications (and listed “con” for them) is that every little piece that may need to be rendered on its own must be broken out into its own template. This pattern eliminates the “locality of behavior” benefits; you cannot even see your entire template together in one place. Fragment rendering eliminates that requirement.

Developing with Giraffe View Engine, we can do part of this out-of-the-box, as we can control the functions we use to create the nodes that will eventually be rendered. And, while there is not a concept of a “template fragment” in Giraffe View Engine, the term “fragment” as applied to an HTML document identifies its id attribute.

Giraffe.ViewEngine.Htmx, as of v1.8.4, now supports rendering these fragments based on the id attribute. Giraffe has the RenderView module where its rendering functions are defined; opening the Giraffe.ViewEngine.Htmx namespace exposes the RenderFragment module. Its functions follow the pattern of Giraffe View Engine:

  • AsString functions return a string
  • AsBytes functions return a byte array
  • IntoStringBuilder functions render into the provided StringBuilder

Each of those three modules has htmlFromNodes if the source is a node list, and htmlFromNode if the source is a single node. (As fragment rendering has little-to-no use in the XML world, XML rendering functions are not provided.)

One final thought - while this was built with htmx applications in mind, the concept does not require htmx. If you want to render fragments with Giraffe View Engine, using this package will allow that, whether your application uses htmx (you probably should!) or not.

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