default-constructor

Macros for creating pseudo-dsls that constructs structs through default construction and field conversion.

Motivation

This crates is primary designed for bevy where constructing large bundles with ..Default::default() is common.

Syntax

Take construct! that uses Into.

construct! {
    Student {
        name: "Timmy",
        age: 10,
        father: Parent {
            name: "Tommy",
            age: 42
        }
    }
}

This expands to

Student {
    name: Into::into("Timmy"),
    age: Into::into(10),
    father: construct! {
        Parent {
            name: "Tommy",
            age: 42
        }
    }
    ..Default::default()
}

The macro is recursive on nested struct declarations, if the behavior is not desired, wrap nested structs in brackets.

construct! {
    Student {
        name: "Timmy",
        age: 10,
        father: { Parent {
            name: "Tommy",
            age: 42
        }}
    }
}

Tuple Construction

To create a tuple, concatenate multiple structs with comma.

construct! {
    Student {
        name: "Timmy",
        age: 10,
    },
    Son::<2> {
        of: "Tommy"
    },
    Age(16),
}

Meta Constructor

The meta constructor macro allows you to define your own macro with custom configurations.

See documentation on meta_default_constructor! for details.

InferInto

InferInto allows the user to bypass the orphan rule to create conversions.

By default we provide i32 (integer literal) to all numeric types and i64 -> f64 in addition to the standard From and Into.

If multiple conversion paths are found, the conversion will fail, thus failing the infer_construct macro.

ChangeLog

• 0.4
  • meta_default_constructor no longer takes a list of imports as the first argument.
  • meta_default_constructor can now create tuples by chaining with comma.

License

License 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.

Contribution

Contributions are welcome!

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.