Trait Document

Source

pub trait Document {
    // Required method
    fn find(&self, key: &str) -> Option<Value<'_>>;
}

Expand description

A Document that can be evaluated by the solver.

Rules are solved against Documents, and thus to solve against a data type it must implement Document. Implementing Object gives this trait for free. Most of the time this trait will not need to be implmented, it is there to enable complex use cases.

§Implementations

The implementation for Object will just pass the find call along to the Object implementation of find. If for some reason this was undesired or just not needed below is an example of how to implement Document.

use std::borrow::Cow;

use tau_engine::{Document, Value};

struct Foo {
    bar: String,
    baz: String,
}

impl Document for Foo {
    fn find(&self, key: &str) -> Option<Value<'_>> {
        match key {
            "bar" => Some(Value::String(Cow::Borrowed(&self.bar))),
            "baz" => Some(Value::String(Cow::Borrowed(&self.baz))),
            _ => None,
        }
    }
}