foo.rs

#[derive(Serialize, Deserialize, Insertable)]
#[table_name="users"]
pub struct NewUser {
    pub name: String,
    pub username: String,
    pub email: String,
    #[serde(rename(deserialize = "password"))]
    #[serde(deserialize_with = "hash_user_password")]
    pub hashed_password: String
}

fn hash_user_password<D>(deserializer: D) -> Result<String, D::Error>
    where D: Deserializer
{
    let password: String = Deserialize::deserialize(deserializer)?;
    hash(&password, DEFAULT_COST)
        .map_err(de::Error::custom)
        .map(|hashed_password|hashed_password)
}