handlebars-rust

Rust templating with Handlebars templating language.

Getting Started

If you are not familiar with handlebars language syntax, it is recommended to walk through their introduction first.

Check render example in the source tree. The example shows you how to:

• Create a Handlebars registry and register the template from files;
• Create a custom Helper with closure or struct implementing HelperDef, and register it;
• Define and prepare some data;
• Render it;

Run cargo run --example render to see results. (or RUST_LOG=handlebars=info cargo run --example render for logging output).

Checkout examples/ for more concrete demos of current API.

From 0.13, you can use either rustc_serialize or serde for your data type. By default we use ToJson from rustc_serialize to convert your data into handlebars internal types. If you use serde framework in your project, you can enable serde_type feature of this crate and we will use Serialize from serde to convert.

Documents

Rust doc.

Changelog

Change log is available in the source tree named as CHANGELOG.md.

Why (this) Handlebars?

Handlebars is a real-world templating system that you can use to build your application without pain.

Features

Isolation of Rust and HTML

This library doesn't attempt to use some macro magic to allow you to write your template within your rust code. I admit that it's fun to do that but it doesn't fit real-world use case.

Limited but essential control structure built-in

Only essential control directive if and each were built-in. This prevents you to put too much application logic into your template.

Extensible helper system

You can write your own helper with Rust! It can be a block helper or inline helper. Put you logic into the helper and don't repeat yourself.

A helper can be as a simple as a Rust function like:

fn hex_helper (h: &Helper, _: &Handlebars, rc: &mut RenderContext) -> Result<(), RenderError> {
    // just for example, add error check for unwrap
    let param = h.param(0).unwrap().value();
    let rendered = format!("0x{:x}", param.as_u64().unwrap());
    try!(rc.writer.write(rendered.into_bytes().as_ref()));
    Ok(())
}

/// register the helper
handlebars.register_helper("hex", Box::new(hex_helper));

And using it in your template:

{{hex my_value}}

Template inheritance

Every time I look into a templating system, I will investigate its support for template inheritance.

Template include is not sufficient for template reuse. In most case you will need a skeleton of page as parent (header, footer, etc.), and embed you page into this parent.

You can find a real example for template inheritance in examples/partials.rs, and templates used by this file.

From 0.23 we support Handlebars 4.0 partial syntax by default. Original partial syntax via block, partial helpers are still supported via feature flag partial_legacy. Examples can be find in examples/partials.rs.

WebAssembly compatible

You can use this handlebars implementation in your rust project that compiles to WebAssembly. Checkout my fork of todomvc demo.

Limitations

• This implementation is not fully compatible with the original javascript version. Specifically, mustache list iteration and null check doesn't work. But you can use #each and #if for same behavior.
• You will need to make your data ToJson-able, so we can render it. If you were on nightly channel, we have a syntax extension to generate default ToJson implementation for you. If you use serde, you can enable serde_type feature of handlebars-rust and add #derive[Serialize] for your types.

Handlebars-js features supported in Handlebars-rust

• Expression / Block Helpers
• Built-in helpers
  • each
  • if
  • with
  • lookup
  • log
• Custom helper
• Parameter and hashes for helper, block params
• Partials, include, template inheritance
• Omitting whitespace with ~
• Subexpression {{(foo bar)}}
• Json expression a.b.[0] and a.b.[c]
• RawHelper syntax {{{{raw-helper}}}}...{{{{/raw-helper}}}}
• Decorator, implemented in Rust way

JavaScript implementation features we don't have

• Mustache block (use if/each instead)
• Chained else

Feel free to report an issue if you find something broken. We aren't going to implement all features of handlebars-js, but we should have a workaround for cases we don't support.

Handlebars for Web Frameworks

• Iron: handlebars-iron
• Rocket: rocket/contrib

Using handlebars-rust?

Add your project to our adopters.

License

This library (handlebars-rust) is open sourced under MIT License.

Contact

Ning Sun (sunng@about.me)