Prelude Pre-import

Will10/30/24About 1 min

Prelude Pre-import Pattern

To improve development efficiency, reduce boilerplate code, and unify code style, our project extensively uses the Prelude pattern. You'll find a prelude.rs file under both model and service modules.

Core Concept

Centralize the most commonly used types, traits, and functions within a module into a prelude.rs file for public export. Other files in the module just need use crate::module::prelude::*; to import all necessary dependencies.

Why Use the Prelude Pattern?

Before Prelude, each service/model file might start with many use statements:

// Verbose import list
use crate::common::error::{Error, Result};
use crate::common::ApiResponse;
use crate::DB;
use sea_orm::{EntityTrait, QueryFilter, Set, ActiveModelTrait};
use serde::Serialize;
use tracing::info;

With Prelude:

// Clean, unified import
use crate::service::prelude::*;

1. `model::prelude` - Foundation of Data Models

Exports core tools for data definition, database operations, and serialization:

SeaORM: EntityTrait, ModelTrait, ActiveModelTrait, QueryFilter, ColumnTrait, Condition, DatabaseConnection, DbErr, PaginatorTrait
Serde: Serialize, Deserialize
Axum: IntoResponse
Project Components: Error, Result, ApiResponse, VJson, VQuery, DB, GID

2. `service::prelude` - Business Logic Hub

Exports everything from model::prelude plus:

Service-level helpers and macros
Common service functions

Usage

use crate::service::prelude::*;

pub struct UserService;

impl UserService {
    pub async fn find_user_by_id(user_id: i64) -> Result<Option<model::user::Model>> {
        let db = DB.get().unwrap();
        let user = model::user::Entity::find_by_id(user_id).one(db).await?;
        Ok(user)
    }
}

Best Practices

Important: About * (Glob Import)

In regular Rust code, wildcard imports are often not recommended. However, in the Prelude pattern, * import is recommended and idiomatic.

When to add to Prelude? When a type/trait is used in over 80% of files in the same module.
When not to add? Types used in only one or two files.
Follow hierarchy: model files use model::prelude::*; service files use service::prelude::*.

Prelude Pre-import