Records in UDL

Our simple TodoEntry is defined in UDL as:

dictionary TodoEntry {
    boolean done;
    u64? due_date;
    string text;
};

All the usual types are supported.

Object references

Our dictionary can refer to obects - here, a User

interface User {
    // Some sort of "user" object that can own todo items
};

dictionary TodoEntry {
    User owner;
    string text;
}

The Rust struct will have owner as an Arc<>.

Optional and compound fields.

Fields can be made optional using a T? type.

dictionary TodoEntry {
    boolean done;
    string? text;
};

The corresponding Rust struct would need to look like this:

struct TodoEntry {
    done: bool,
    text: Option<String>,
}

You can similarly use a HashMap, Vec<> etc.

dictionary TodoEntry {
    sequence<string> item_list;
    record<string, string> item_map;
};

Default values for fields

Fields can be specified with a default literal value.

dictionary TodoEntry {
    boolean done = false;
    string text = "unnamed";
};

An Option<> can be specified as null or an appropriate literal for a Some value. HashMap and Vec have custom syntax.

dictionary TodoEntry {
    string? text = null;
    string? alt_text = "unnamed"
    sequence<string> item_list = [];
    record<string, string> item_map = {};
};