Gel Rust Binding: Derive Crate

This crate contains derive macros for the Gel client.

• Documentation
• Tokio Client

License

Licensed under either of

• Apache License, Version 2.0, (./LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (./LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

lib.rs:

Derive macro that allows structs and enums to be populated by database queries.

This derive can be used on structures with named fields (which correspond to "shapes" in Gel). Note that field order matters, so the struct below corresponds to an Gel User query with first_name followed by age. A DescriptorMismatch will be returned if the fields in the Rust struct are not in the same order as those in the query shape.

#[derive(Queryable)]
struct User {
first_name: String,
age: i32,
}

This allows a query to directly unpack into the type instead of working with the Value enum.

let query = "select User { first_name, age };";
// With Queryable:
let query_res: Vec<User> = client.query(query, &()).await?;
// Without Queryable:
let query_res: Vec<Value> = client.query(query, &()).await?;

Field attributes

JSON

The #[gel(json)] attribute decodes a field using serde_json instead of the Gel binary protocol. This is useful if some data is stored in the database as JSON, but you need to process it. The underlying type must implement serde::Deserialize.

#[derive(Queryable)]
struct User {
#[gel(json)]
user_notes: HashMap<String, String>,
}

Container attributes

JSON

The #[gel(json)] attribute can be used to unpack the structure from the returned JSON. The underlying type must implement serde::Deserialize.

#[derive(Queryable, serde::Deserialize)]
#[gel(json)]
struct JsonData {
field1: String,
field2: u32,
}

This allows a query to directly unpack into the type without an intermediate step using serde_json::from_str:

let query = "select <json>JsonData { field1, field2 };";
let query_res: Vec<JsonData> = client.query(query, &()).await?;