Attribute Macro model

#[model]

Available on crate feature db only.

Implement the Model trait for a struct.

This macro will generate an implementation of the Model trait for the given named struct. Note that all the fields of the struct must implement the DatabaseField trait.

Model types

The model type can be specified using the model_type parameter. The model type can be one of the following:

• application (default): The model represents an actual table in a normally running instance of the application.

use cot::db::model;

#[model(model_type = "application")]
// This is equivalent to:
// #[model]
struct User {
    #[model(primary_key)]
    id: i32,
    username: String,
}

• migration: The model represents a table that is used for migrations. The model name must be prefixed with an underscore. You shouldn’t ever need to use this type; the migration engine will generate the migration model types for you.

  Migration models have two major uses. The first is so that the migration engine uses knows what was the state of model at the time the last migration was generated. This allows the engine to automatically detect the changes and generate the necessary migration code. The second use is to allow custom code in the migrations: you might want the migration to fill in some data, for instance. You can’t use the actual model for this because the model might have changed since the migration was generated. You can, however, use the migration model, which will always represent the state of the model at the time the migration runs.

// In a migration file
use cot::db::model;

#[model(model_type = "migration")]
struct _User {
    #[model(primary_key)]
    id: i32,
    username: String,
}

• internal: The model represents a table that is used internally by Cot (e.g. the cot__migrations table, storing which migrations have been applied). They are ignored by the migration generator and should never be used outside Cot code.

use cot::db::model;

#[model(model_type = "internal")]
struct CotMigrations {
    #[model(primary_key)]
    id: i32,
    app: String,
    name: String,
}