Another post, another long delay. In my last post I teased that I'd been working on another extension to Stubble which would add handlebars style helpers to your mustache templates.

This extension while simple has some fun complexity in terms of how people may want to use this in a strongly typed manner unlike handlebars. A nice simple example is this:

var culture = new CultureInfo("en-GB");
var helpers = new Helpers()
    .Register("FormatCurrency", (HelperContext context, decimal count) => count.ToString("C", culture));

var stubble = new StubbleBuilder()
    .Configure(conf => conf.AddHelpers(helpers))
    .Build();

var result = stubble.Render("{{FormatCurrency Count}}", new { Count = 100.26m });

Assert.Equal("£100.26", result);

Hopefully it's clear that this helper allows the user to add their own non-standard tag-style to their templates which has custom functionality which in this case formats a decimal with a specific culture.

There's also a slightly more advanced case where you can access a slimmed version of the render context to access any variable in your object by name. This gives you more control but also more chances for things exploding at runtime.

var helpers = new Helpers()
    .Register("PrintListWithComma", (context) => string.Join(", ", context.Lookup<int[]>("List")));

var builder = new StubbleBuilder()
    .Configure(conf => conf.AddHelpers(helpers))
    .Build();

var res = builder.Render("List: {{PrintListWithComma}}", new { List = new[] { 1, 2, 3 } });

Assert.Equal("List: 1, 2, 3", res);

You can also have static arguments in your template that will be passed into your helper. There are some caveats to this which I'll note below the example:

var culture = new CultureInfo("en-GB");
var helpers = new Helpers()
    .Register("FormatCurrency", (HelperContext context, decimal count) => count.ToString("C", culture));

var stubble = new StubbleBuilder()
    .Configure(conf => conf.AddHelpers(helpers))
    .Build();

var result = stubble.Render("{{FormatCurrency 10}}", new { });

Assert.Equal("£10.00", result);

Cavets

• The type should match or be convertable to the argument type.
• If you're writing a constant string as an argument then it should be escaped with quotes either " or '. Quoted strings are treated as verbatim and will not be attempted to be looked up in the context however their type will still be converted.
• If you have a quote in your string for example It's then you can escape it with a / like so: It/'s.

Stubble's Extension Philosophy

While writing this I was going to expand on why I didn't include this in the main Stubble package along with some thoughts on creating libraries based on standards and how/where to deviate/extend from that standard. If this doesn't interest you then thanks for reading this post, if it does then please see my post on Stubble extensions and enhancements here.