Trait frunk_core::labelled::Transmogrifier[−][src]

pub trait Transmogrifier<Target, TransmogrifyIndexIndices> {
    fn transmogrify(self) -> Target;
}
Expand description

Trait for transmogrifying a Source type into a Target type.

What is “transmogrifying”? In this context, it means to convert some data of type A into data of type B, in a typesafe, recursive way, as long as A and B are “similarly-shaped”. In other words, as long as B’s fields and their subfields are subsets of A’s fields and their respective subfields, then A can be turned into B.

Example

#[macro_use] extern crate frunk;
#[macro_use] extern crate frunk_core; // required when using custom derives
use frunk::labelled::Transmogrifier;
#[derive(LabelledGeneric)]
struct InternalPhoneNumber {
    emergency: Option<usize>,
    main: usize,
    secondary: Option<usize>,
}

#[derive(LabelledGeneric)]
struct InternalAddress<'a> {
    is_whitelisted: bool,
    name: &'a str,
    phone: InternalPhoneNumber,
}

#[derive(LabelledGeneric)]
struct InternalUser<'a> {
    name: &'a str,
    age: usize,
    address: InternalAddress<'a>,
    is_banned: bool,
}

#[derive(LabelledGeneric, PartialEq, Debug)]
struct ExternalPhoneNumber {
    main: usize,
}

#[derive(LabelledGeneric, PartialEq, Debug)]
struct ExternalAddress<'a> {
    name: &'a str,
    phone: ExternalPhoneNumber,
}

#[derive(LabelledGeneric, PartialEq, Debug)]
struct ExternalUser<'a> {
    age: usize,
    address: ExternalAddress<'a>,
    name: &'a str,
}

let internal_user = InternalUser {
    name: "John",
    age: 10,
    address: InternalAddress {
        is_whitelisted: true,
        name: "somewhere out there",
        phone: InternalPhoneNumber {
            main: 1234,
            secondary: None,
            emergency: Some(5678),
        },
    },
    is_banned: true,
};

/// Boilerplate-free conversion of a top-level InternalUser into an
/// ExternalUser, taking care of subfield conversions as well.
let external_user: ExternalUser = internal_user.transmogrify();

let expected_external_user = ExternalUser {
    name: "John",
    age: 10,
    address: ExternalAddress {
        name: "somewhere out there",
        phone: ExternalPhoneNumber {
            main: 1234,
        },
    }
};

assert_eq!(external_user, expected_external_user);
Run

Credit:

  1. Haskell “transmogrify” Github repo: https://github.com/ivan-m/transmogrify

Required methods

Consume this current object and return an object of the Target type.

Although similar to sculpting, transmogrifying does its job recursively.

Implementors