Auto-Generating IDs

In the last chapter, users had to specify their own IDs. That’s not ideal - what if two users pick the same ID?

Let’s make IDs generate automatically using UUIDs.

The Problem

# User has to pick an ID - what if 1 is already taken?
curl -X POST http://localhost:3000/tasks \
  -d '{"id": 1, "title": "My task"}'

The Solution

Two changes:

1. Exclude the ID from create requests
2. Auto-generate it with on_create

use uuid::Uuid;

#[derive(Clone, Debug, DeriveEntityModel, EntityToModels)]
#[crudcrate(generate_router)]
#[sea_orm(table_name = "tasks")]
pub struct Model {
    #[sea_orm(primary_key, auto_increment = false)]
    #[crudcrate(
        primary_key,
        exclude(create, update),      // Users can't set or change ID
        on_create = Uuid::new_v4()    // Generate UUID automatically
    )]
    pub id: Uuid,

    pub title: String,
}

Add uuid to your Cargo.toml:

uuid = { version = "1.0", features = ["v4", "serde"] }

Update your table:

CREATE TABLE tasks (
    id TEXT PRIMARY KEY,
    title TEXT NOT NULL
)

Now It Works

# No ID needed!
curl -X POST http://localhost:3000/tasks \
  -H "Content-Type: application/json" \
  -d '{"title": "Buy groceries"}'

Response - ID is generated:

{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "title": "Buy groceries"
}

What exclude Does

What on_create Does

📋 See test

The expression is evaluated when inserting a new record:

on_create = Uuid::new_v4()      // Generate UUID
on_create = chrono::Utc::now()  // Current timestamp
on_create = 0                   // Default number
on_create = false               // Default boolean

Our Task Model Now

pub struct Model {
    #[crudcrate(primary_key, exclude(create, update), on_create = Uuid::new_v4())]
    pub id: Uuid,

    pub title: String,
}

But when was this task created? When was it last updated? We have no idea.

Next: Let’s add timestamps to track when things happen.