Variables

Template variables are closer to constants than variables, since they can not be reassigned.

There are two kinds:

• Global
• Local

A local value will always shadow a global value with the same name, and with / for will always shadow local values.

Global

Globals are defined using the global keyword: global <ident> = <expression> and they are global across all templates.

Once a global is defined it can not be re-defined. Trying to define a global twice will result in an error.

Runtime Globals

Globals can be registered with the runtime as well.

Registering a global with the same name twice will result in an error.

Example

#![allow(unused)]
fn main() {
let mut builder = Runtime::builder(doc, &backend);
builder.register_global("string_value", "hello").unwrap();
builder.register_global("num_value", 123).unwrap();
builder.register_global("a_list", [1, 2, 3]).unwrap();
}

vstack
    text string_value
    text num_value
    for i in a_list
        text i

Example

global value = 1
text value

Notes

Global values can be defined anywhere in the template, but it's best practice to place them at the to of the template.

Local

The old let keyword is now an alias for local.

Locals are defined using the local keyword: local <ident> = <expression>.

A local value is never accessible outside the current component, and is scoped to the parent element.

Example

local value = 1
text value

Notes

Unlike globals the placement within the template is relevant for locals.

The following will display 1:

local x = 1
vstack
    text x

The following template

local x = 1
vstack
    text x
    vstack
        local x = 2
        text x
    text x

will display

1
2
1