Timestamps

Timestamp fields are output-only fields, automatically populated by a schema-level resolver when a record is created or updated.

• #[created_at] -- set once, at creation.
• #[updated_at] -- set at creation and on every update.
• #[optional_updated_at] -- like #[updated_at], but typed Option<T> and only ever set once an update actually happens; stays None until then.
• A schema may declare zero or one of each. Both use the same shared, synchronous resolver, declared once via #[timestamps(|| ...)] (or a bare function path) on an anonymous const item.
• Requires output(...) on the schema, since timestamps never appear on the input struct.

Example: default field names

use chrono::{DateTime, Utc};
use ivo::ivo_schema;

type Timestamp = DateTime<Utc>;

#[ivo_schema(
    input(DataInput, derive(Debug, Clone, PartialEq)),
    output(Data, derive(Debug, Clone, PartialEq))
)]
mod timestamps_schema {
    use super::Timestamp;
    use chrono::Utc;

    struct Fields {
        #[lax("default_username".to_string())]
        pub username: String,

        #[created_at]
        pub created_at: Timestamp,

        #[updated_at]
        pub updated_at: Timestamp,
    }

    #[timestamps(|| Utc::now())]
    const _: () = ();
}

fn main() {
    let (created, _ctx_options) = timestamps_schema::DataModel
        .create(timestamps_schema::PartialDataInput { username: None }, ())
        .unwrap();

    println!("{:#?}", created);
    // Data { username: "default_username", created_at: ..., updated_at: ... }
    // created_at == updated_at right after creation
}

Example: custom field names, optional updated_at

Timestamp fields can be named anything -- the attribute, not the field name, is what matters. Use #[optional_updated_at] when "never updated yet" should be a real, distinct None state rather than defaulting to the creation timestamp:

struct Fields {
    #[lax("default_username".to_string())]
    pub username: String,

    #[created_at]
    pub inserted_at: Timestamp,

    #[optional_updated_at]
    pub modified_at: Option<Timestamp>,
}

modified_at is None on the freshly created record, and only becomes Some(...) after the first update.

More examples

• Default names
• Custom names

Try it in the browser

username is a lax field with a default. created_at and updated_at are populated automatically from the timestamp resolver.

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