#has_many

🏭 Macro

#[has_many($struct_name.$struct_foreign_key)]

Implements a has-many relationship between the current entity and another entity. The $struct_name is the name of the other entity and the $struct_foreign_key is the field on that entity which should equal the ID of this entity. This macro is just a convenient way to set up the relationship by implementing the HasManyForeignKey.

📝 Macro Example:

use repox::Entity;

#[derive(Debug, Clone, PartialEq, Entity)]
#[has_many(Post.author_id)]   // <- Author has many Posts via Post.author_id
pub struct Author {
    pub id: u32,
    pub name: String,
}

#[derive(Debug, Clone, PartialEq, Entity)]
pub struct Post {
    pub id: u64,
    pub author_id: u32,
    pub data: String,
}

// Quick Demo of the relationship in action:
let alice = Author { id: 1, name: "Alice".to_string() };
let darin = Author { id: 2, name: "Darin".to_string() };
let post = Post { id: 100, author_id: 1, data: "Hello World".to_string() };
assert!(alice.is_owner_of(&post));
assert!(!darin.is_owner_of(&post));
assert_eq!(alice.has_many_key::<Post>(&post), 1);

🔬 Macro Details:

Here is the same example, but, without using the macro. You can see that it’s just a convenient way to set up the relationship by implementing HasManyForeignKey for you.

use repox::Entity;

#[derive(Debug, Clone, PartialEq, Entity)]
pub struct Author {
    pub id: u32,
    pub name: String,
}

#[derive(Debug, Clone, PartialEq, Entity)]
pub struct Post {
    pub id: u64,
    pub author_id: u32,
    pub data: String,
}

// this is what the #[has_many(Post.author_id)] macro expands to:
impl repox::HasManyForeignKey<Post> for Author {
    fn key(entity: &Post) -> <Author as repox::Identity>::ID {
        entity.author_id
    }
}

// Quick Demo of the relationship in action:
let alice = Author { id: 1, name: "Alice".to_string() };
let darin = Author { id: 2, name: "Darin".to_string() };
let post = Post { id: 100, author_id: 1, data: "Hello World".to_string() };
assert!(alice.is_owner_of(&post));
assert!(!darin.is_owner_of(&post));
assert_eq!(alice.has_many_key::<Post>(&post), 1);