Crate rsb_derive

Rust struct builder implementation macro

Motivation

A derive macros to support a builder pattern for Rust:

• Everything except Option<> fields and explicitly defined default attribute in structs are required, so you don’t need any additional attributes to indicate it, and the presence of required params is checked at the compile time (not at the runtime).
• To create new struct instances there is ::new and an auxiliary init struct definition with only required fields (to compensate the Rust’s named params inability).

Usage:

// Import it
use rsb_derive::Builder;

// And use it on your structs
#[derive(Clone,Builder)]
struct MyStructure {
    pub req_field1: String,
    pub req_field2: i32,
    pub opt_field1: Option<String>,
    pub opt_field2: Option<i32>
}

let s1 : MyStructure =
    MyStructure::from(
        MyStructureInit {
             req_field1 : "hey".into(),
             req_field2 : 0
        }
    )
    .with_opt_field1("hey".into())
    .with_opt_field2(10);

The macros generates the following functions and instances for your structures:

• with/without_<field_name> : immutable setters for fields
• <field_name>/reset_<field_name> : mutable setters for fields
• new : factory method with required fields as arguments
• From<> instance from an an auxiliary init struct definition with only required fields. The init structure generated as <YourStructureName>Init. So, you can use from(...) or into() functions from it.

Defaults

use rsb_derive::Builder;

#[derive(Debug, Clone, PartialEq, Builder)]
struct StructWithDefault {
    pub req_field1: String,
    #[default="10"]
    pub req_field2: i32, // default here make this field behave like optional

    pub opt_field1: Option<String>,
    #[default="Some(11)"]
    pub opt_field2: Option<i32> // default works also on optional fields
}

Details and source code: [https://github.com/abdolence/rust-struct-builder]: https://github.com/abdolence/rust-struct-builder

Derive Macros

Builder