Crate field_ref

GetField reference (like a member pointer to non-static data field in C++) for Rust

Examples

Subfield of type U which is contained by T can be obtained via FieldRef<T, U>.

use field_ref::{GetField, GetFieldMut, field_ref_of};

struct Foo(u32, u32, f64);
struct Bar {
    foo: Foo,
    x: u32,
}

let fr1 = field_ref_of!(Bar => x);
let fr2 = field_ref_of!(Bar => foo);
let fr3 = field_ref_of!(Foo => 1);
let fr4 = field_ref_of!(Bar => foo => 0);

let mut bar = Bar { foo: Foo(10, 20, 0.5), x: 30 };

assert_eq!(bar.get_field(fr1), &30);
assert_eq!(fr1.get(&bar), &30);

*bar.get_field_mut(fr1) = 100;
assert_eq!(bar.x, 100);

*fr1.get_mut(&mut bar) = 200;
assert_eq!(bar.x, 200);

assert_eq!(bar.get_field(fr2.chain(fr3)), &20);
assert_eq!(bar.get_field(fr4), &10);

Enum field of type T can be obtain as Option<&T> via OptionFieldRef. Other field such as struct field of type T can also be obtain as Option<&T> via OptionFieldRef.

use field_ref::{GetField, GetFieldMut, OptionFieldRef, opt_field_ref_of};

struct Foo {
    x: i32,
    y: f64,
}

enum E1 {
    A(i32),
    B(i32, Foo),
}

enum E2 {
    X(E1),
    Y,
}

let fr1 = opt_field_ref_of!(E1::A{0});
let fr2 = opt_field_ref_of!(E2::X{0} & E1::B{1} => y);
let fr3 = opt_field_ref_of!(Foo => x);

let e1_1 = E1::A(10);
let e1_2 = E1::B(20, Foo{ x: 25, y: 2.5 });
let e2_1 = E2::X(E1::B(10, Foo{ x: 30, y: 3.5 }));
let e2_2 = E2::Y;

let mut foo = Foo{ x: 40, y: 4.5 };

assert_eq!(e1_1.try_get_field(fr1), Some(&10));
assert_eq!(e1_2.try_get_field(fr1), None);

assert_eq!(e2_1.try_get_field(fr2), Some(&3.5));
assert_eq!(e2_2.try_get_field(fr2), None);

assert_eq!(foo.try_get_field(fr3), Some(&40));
*foo.try_get_field_mut(fr3).unwrap() = 50;
assert_eq!(foo.x, 50)

Macros

field_ref_of	Creates a new FieldRef from basic type and fields which are (recursively) contained by that type.
opt_field_ref_of	Creates a new instance of OptionFieldRef from basic type (enum constansts, structs or tuples) and these fields.

Structs

EnumFieldRef	A OptionFieldRef references a field within an enum constant.
FieldRef	A reference to field of type U (recursively) contained by an object of type T.
FieldRefAsOptionFieldRef	A OptionFieldRef which converted from A FieldRef.
OptionFieldRefChain	A OptionFieldRef which chains two OptionFieldRefs.

Traits

GetField	A trait to obtain a value to which FieldRef references via description like obj.get_field(field_ref).
GetFieldMut	A trait to obtain a mutable value to which FieldRef references via description like obj.get_field_mut(field_ref).
OptionFieldRef	A reference to field of type Input (recursively) contained by an object of type Output and that may fail dereference.