References

Zmpl uses a simple but powerful system for references (also known as "template variables").

References are delimited by {{ and }}:

@zig {
    const foobar = "hello";
}

<div>{{foobar}}</div>

If the given value can be safely coerced to a string then the output is rendered accordingly.

Since Zmpl templates are compiled into Zig functions, you get all the benefits of the Zig compiler such as:

• Unrecognized variables result in an error.
• Unused variables also raise an error.
• Backtraces for all errors (note that backtraces come from the compiled Zmpl template, but they generally will give you enough information to solve issues).

There are three main types of data references:

• Data lookups
• Variable/constant references
• Zig code

Data lookups

If a reference begins with a . character then it is considered a data lookup. Use this syntax when you need to access any values added to the data argument passed to every View function.

For example:

const jetzig = @import("jetzig");

pub fn index(request: *jetzig.Request) !jetzig.View {
    var root = try request.data(.object);
    try root.put("message", "Welcome to Jetzig!");
    try root.put("iguana_count", 100_000);

    return request.render(.ok);
}

Important: The first call to request.data() sets the root value. All data references use this value as their starting point. You should only call this once per request unless you specifically wish to re-initialize the root value.

These values can now be accessed in a Zmpl template:

<div>{{.message}}</div>
<div>We found {{.iguana_count}} iguanas!</div>

This syntax can also be used to access nested keys:

const jetzig = @import("jetzig");

pub fn index(request: *jetzig.Request) !jetzig.View {
    var root = try request.data(.object);

    var iguana = try root.put(.object);
    try iguana.put("name", "Ziggy");

    return request.render(.ok);
}

The iguana's name can now be accessed in a template:

<div>The iguana is named {{.iguana.name}}</div>

Variable/constant references

All references that do not begin with . are assumed to reference a value in the current scope assigned in one of three ways:

• By the template code itself in a zig mode section.
• By Jettzig (e.g. the jetzig_view and jetzig_action constants available in every template).
• Arguments passed to a partial.

@zig {
    const red = "#ff0000";
}
<div style="color: {{color}}">Some red text</div>

Zig code

If needed, arbitrary Zig code can be used inside a reference. Note that this code must evaluate to a []const u8:

<div>{{if (true) "foo" else "bar"}}</div>