This Swift package provides two types, Box and BoxObject.
Box is a value type that wraps another value type for heap allocation like Rust's Box. Also, it is implemented with copy-on-write behavior.
BoxObject is almost the same as Box, but it's a reference type. If you copy the wrapped value, you can call its copy() method.
import Box
struct Foo {
@Box var a: Int
var b: Box<Int>
var c: BoxObject<Int>
}
var foo = Foo(a: 3, b: .init(4), c: .init(9))
print(foo) // Foo(_a: 3, b: 4, c: 9)
var bar = foo
bar.a = 10
bar.b.value = 5
bar.c.value = 99
print(foo) // Foo(_a: 3, b: 4, c: 99)
print(bar) // Foo(_a: 10, b: 5, c: 99)