API Doc

Diesel Enum Derivation for FromSql and ToSql

This procedural macro simplifies the process of generating Diesel FromSql and ToSql instances for enums with a specific SqlType. It is designed for use with Diesel and Postgres, utilizing ToString and FromStr traits as the base for conversion. This macro generates the necessary boilerplate code for handling enum conversions between Rust and SQL.

Table of Contents

• Usage
• Example
• Enums and SqlTypes
• Dependencies

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Usage

To use this procedural macro, you'll need to add the enum_diesel_macros crate to your project's dependencies in Cargo.toml. You can then derive the necessary implementations for your enums. Below is an example of how to use the FromToSql macro:

#[derive(Debug, PartialEq, EnumString, Display, FromToSql)]
#[fromtosql(sql_type = MyEntityEnumSqlType)]
enum MyEntityEnum {
    #[strum(serialize = "ONE")]
    EnumOne,
    #[strum(serialize = "TWO")]
    EnumTwo,
}

Make sure to import the required dependencies and modules as shown in the example.

Example

Here's a step-by-step example of how to use the FromToSql macro to generate Diesel FromSql and ToSql instances for your enum:

1. Define your custom SQL type using Diesel's SqlType and annotate it with diesel attributes:

pub mod schema {
    pub mod sql_types {
        #[derive(diesel::sql_types::SqlType)]
        #[diesel(postgres_type(name = "myentittyenumsqltype", schema = "myschema"))]
        pub struct MyEntityEnumSqlType;
    }
}

2. Import the necessary Diesel and procedural macro dependencies:

#[derive(Debug, PartialEq, EnumString, Display, FromToSql)]
#[fromtosql(sql_type = MyEntityEnumSqlType)]
enum MyEntityEnum {
    #[strum(serialize = "ONE")]
    EnumOne,
    #[strum(serialize = "TWO")]
    EnumTwo,
}

3. Now, you can use your MyEntityEnum enum seamlessly with Diesel queries.

Enums and SqlTypes

The key to using this macro is to ensure that you have a corresponding SqlType defined for your enum. In this example, MyEntityEnumSqlType represents the SQL type for the MyEntityEnum enum. This SqlType is generated in Diesel schemas and serves as the companion enum to MyEntityEnum.

Ensure that your enum also implements either the FromStr or EnumString trait, which is crucial for parsing the enum from SQL values.

Dependencies

To use this procedural macro, make sure to include the following dependencies in your Cargo.toml:

[dependencies]
diesel = { version = "2.1", features = ["postgres"] }
strum = "0.25"
strum_macros = "0.25"
diesel-sqltype-enum-pg = "0.1.0"