Parameter Binding & the Params Trait
Template::bind takes anything that implements anza::Params
(src/engine/slot/bind.rs). The builders (Page, Fragment, Stream) and the
Engine::render_* methods always use HashMap<String, String>; the other
implementations are for binding a template yourself with engine.get(name)?.bind(...).
1. The trait
use std::borrow::Cow;
pub trait Params {
fn resolve(&self, key: &str) -> Option<Cow<'_, str>>;
// Optional hooks with default implementations, used by the built-in types
// to bind faster: prepare() (convert once per bind), indexed() and fill()
// (resolve every name in one pass). Implementing `resolve` is enough.
}Cow::Borrowed lets a value be copied straight from your data without an extra
String; Cow::Owned is for values that must be formatted (numbers, dates).
Returning None renders the placeholder as an empty string.
2. Built-in implementations
| Type | Notes |
|---|---|
() | No values |
[(&str, &str); N] and [(&str, &str)] | Linear search; no allocation |
HashMap<String, String> | Borrowed values |
serde_json::Value | Object keys; booleans as true/false, integral floats without .0 (3.0 → 3), null is empty, arrays/objects as compact JSON |
Data<T: Serialize> | Serializes T to a serde_json::Value once per bind |
&T where T: Params | Forwards |
use std::collections::HashMap;
use anza::Data;
let tpl = engine.get("feed/card.html")?;
let html = tpl.bind(&[("title", "STUI Guide"), ("author", "Sarah")])?;
let html = tpl.bind(&())?;
let mut map = HashMap::new();
map.insert("title".to_string(), "Dynamic Title".to_string());
let html = tpl.bind(&map)?;
let html = tpl.bind(&serde_json::json!({ "title": "From JSON", "count": 3 }))?;
// Any Serialize value (equivalent to tpl.render(&profile)):
let html = tpl.bind(&Data(&profile))?;HashMap<&str, &str> does not implement Params; use an array of pairs or
HashMap<String, String>.
By default all values are inserted without HTML escaping: escape untrusted
input with anza::escape_html first. With Setup::escape on, {{name}}
values are escaped for you and {{{name}}} values stay raw.