model-mapper 0.7.1

Derive macro to map between different types
Documentation 
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#![allow(dead_code, unused)]

use model_mapper::Mapper;

#[derive(Debug, Clone, PartialEq, Eq)]
struct Foo {
    field1: String,
    field2: i64,
    field3: i64,
    field4: Option<String>,
}

// Additional fields doesn't affect 'from' derives, they're just ignored
#[derive(Debug, PartialEq, Eq, Mapper)]
#[mapper(from(custom), ty = Foo, add(field = field3), add(field = field4))]
struct Bar1 {
    field1: String,
    field2: i64,
    // But we can use them on other skipped fields
    #[mapper(skip(default(value = field3 * 2)))]
    field5: i64,
    // And we must be careful if there's some field with the same name
    #[mapper(rename = new_field3, skip)]
    field3: Option<i64>,
}

// For 'into' derives
#[derive(Mapper)]
#[mapper(
    into,
    ty = Foo,
    // We can populate fields using other values, even skipped ones
    add(field = field3, default(value = field5 / 2)),
    // Or just with the default, None in this case
    add(field = field4, default)
)]
struct Bar2 {
    field1: String,
    field2: i64,
    #[mapper(skip)]
    field5: i64,
}

#[derive(Mapper)]
#[mapper(
    // We can also implement a custom function that will require the additional fields at runtime, providing types
    into(custom = "into_foo_custom"), 
    ty = Foo,
    add(field = field3, ty = i64),
    add(field = field4, ty = "Option<String>"), // we might need to quote types
)]
struct Bar3 {
    field1: String,
    field2: i64,
    // But be careful if the type already has another field with the same name that shall not be used
    #[mapper(rename = ignore, skip)]
    field3: Option<i64>,
}

#[derive(Mapper)]
#[mapper(
    // Or even mix both options
    into(custom),
    ty = Foo,
    add(field = field3, default(value = field2 / 2)),
    add(field = field4, ty = "Option<String>"),
)]
struct Bar4 {
    field1: String,
    field2: i64,
}

enum FooEnum {
    One,
    Two,
    Three,
    Four,
}

// For enums, the 'into' derive doesn't require anything but the 'from' requires to provide default values or to
// implement the default trait
#[derive(Default, Mapper)]
#[mapper(
    from,
    ty = FooEnum,
    // We can populate fields using some value
    add(field = Three, default(value = BarEnum::Two)),
    // Or just with the default, One in this case
    add(field = Four, default)
)]
enum BarEnum {
    #[default]
    One,
    Two,
}

fn main() {
    let expected = Foo {
        field1: "val".into(),
        field2: 2,
        field3: 1,
        field4: None,
    };

    let bar = Bar1 {
        field1: "val".into(),
        field2: 2,
        field5: 2,
        field3: Some(7),
    };
    let mapped = Bar1::from_foo(expected.clone(), Some(7));
    assert_eq!(bar, mapped);

    let bar = Bar2 {
        field1: "val".into(),
        field2: 2,
        field5: 2,
    };
    let mapped = bar.into();
    assert_eq!(expected, mapped);

    let bar = Bar3 {
        field1: "val".into(),
        field2: 2,
        field3: None,
    };
    let mapped = bar.into_foo_custom(1, None);
    assert_eq!(expected, mapped);

    let bar = Bar4 {
        field1: "val".into(),
        field2: 2,
    };
    let mapped = bar.into_foo(None);
    assert_eq!(expected, mapped);
}