The File DataSeeder

A data seeder is responsible for seeding data into a state once loaded.

The File data seeder loads the content of a file and set it to the state. It is agnostic to the format of the file. It is up to the user to make sure the format of the file complies to the State requirements.

The Default state, for example, requires the data to be of a certain JSON format:

{
  "cat": {
    "value": "garfield",
    "ttl": 3600000
  },
  "dog": {
    "value": "snoopy"
  }
}

The DataSeeder Trait

#![allow(unused)]
fn main() {
pub trait DataSeeder: std::fmt::Debug + Send + Sync {
    fn load(&self) -> Result<Box<dyn StateValue>, Box<dyn StdError>>;
}

}

We are required to implement the load function and return anything that implements the StateValue trait. If you recall, the StateValue trait requires us to implement a function that deserializes our value into a u8 vector.

#![allow(unused)]
fn main() {
pub trait StateValue: Send + Sync {
    fn as_bytes(&self) -> Option<Vec<u8>>;
}
}

The File DataSeeder

#![allow(unused)]
fn main() {
#[derive(Serialize, Deserialize, Debug)]
pub struct File {
    filename: String,
}

#[typetag::serde]
impl data_seeder::DataSeeder for File {
    fn load(&self) -> Result<Box<dyn StateValue>> {
        let data: Box<dyn StateValue> = Box::new(fs::read(&self.filename)?);
        Ok(data)
    }
}
}

The File data seeder expects a filename to be specified in its configuration. When the load function is called it will read the file and return the data, which complies with the StateValue trait.