Redb模型

用于生成redb表定义和DTO对象转换方法/实现的推导宏。

功能

该软件包旨在统一数据库条目DTO定义和redb::TableDefinition。使用#[derive(Model)]装饰结构体将为类型实现Model，定义redb::TableDefinition作为关联常量，并为类型生成辅助方法。

示例

#[derive(Model)]
struct User {
    #[entry(position(key))]
    id: u32,
    #[entry(position(value))]
    name: String,
    #[entry(position(value))]
    email: String,
}

let user = User {
    id: 0,
    name: "User".to_owned(),
    email: "[email protected]".to_owned(),
};

let txn = db.begin_write().unwrap();
{
    let mut table = txn.open_table(User::DEFINITION).unwrap();
    let (k, v) = user.as_values();
    table.insert(k, v).unwrap();
}
txn.commit().unwrap();

指定键和值

键和值通过使用#[entry(position(...))]装饰表字段来指定，通过将key或value传递给内部字段。复合键/值将组合成一个元组。

#[derive(Model)]
struct User {
    #[entry(position(key))]
    uuid: [u8; 16],
    #[entry(position(value))]
    username: String,
    #[entry(position(value))]
    email: String,
}

let user_key = [0; 16];
let user_value = ("my_name".to_string(), "[email protected]".to_string());

let user = User::from_values((user_key, user_value));
let (k, v) = user.into_values();

// Only the value is a tuple for this model.
assert_eq!(k, [0; 16]);
assert_eq!(v, ("my_name".to_string(), "[email protected]".to_string()));

指定表名

表名默认为（区分大小写）的结构名称。可以通过在结构体上装饰 #[model(name = "...")] 属性来覆盖。

#[derive(Model)]
#[model(name = "user_table")]
struct User {
    #[entry(position(key))]
    uuid: [u8; 16],
    #[entry(position(value))]
    username: String,
}

assert_eq!(User::DEFINITION.name(), "user_table");

类型转换

Model 特性的生成实现提供了实例化、借用和获取模型 DTO 的键/值对的方法。通过在结构体上装饰 #[model(impl_from)] 将进一步实现 From<T>，将 T 映射到 from_values(T) 和 from_guards(T) 方法。

#[derive(Model)]
#[model(impl_from)]
struct User {
    #[entry(position(key))]
    uuid: [u8; 16],
    #[entry(position(value))]
    username: String,
    #[entry(position(value))]
    email: String,
}

let user_key = [0; 16];
let user_value = ("my_name".to_string(), "[email protected]".to_string());

let user: User = ((user_key, user_value)).into();

const TABLE: TableDefinition<(String, String), ()> = TableDefinition::new("table");

let string_0 = "string_0".to_string();
let string_1 = "string_1".to_string();

let txn = db.begin_write().unwrap();
let mut table = txn.open_table(TABLE).unwrap();
// This doesn't work.
table.insert((&string_0, &string_1), ());
// Neither does this.
table.insert((string_0.as_str(), string_1.as_str()), ());
```rust

### Unit type values

The unit type `()` must be passed if no value is defined.
```rust
#[derive(Model)]
#[model(name = "outbound_edge")]
struct Edge {
    #[entry(position(key))]
    source: [u8; 16],
    #[entry(position(key))]
    target: [u8; 16],
}
let k = ([0; 16], [1; 16]);
let v = ();
let e = Edge::from_values((k, v));