Top-level enum

SuperStruct generates an enum that combines all of the generated variant structs.

Consider the MyStruct example from the previous page:

#![allow(unused)]
fn main() {
#[superstruct(variants(Foo, Bar))]
struct MyStruct {
    name: String,
    #[superstruct(only(Foo))]
    location: u16,
}
}

The generated enum is:

#![allow(unused)]
fn main() {
enum MyStruct {
    Foo(MyStructFoo),
    Bar(MyStructBar),
}
}

The enum has one variant per variant in superstruct(variants(..)), and each variant contains its generated variant struct. It is named {BaseName}.

Generation of the top-level enum can be disabled using the no_enum attribute. For more information see the Struct attributes.

Getters and setters

The top-level enum has getters and setters for each of the variant fields. They are named:

{field_name}() for getters.
{field_name}_mut() for setters.

If a field is common to all variants, then the getters and setters are total and return &T and &mut T respectively, where T is the type of the field.

If a field is part of some variants but not others, then the getters and setters are partial and return Result<&T, E> and Result<&mut T, E> respectively.

Many aspects of the getters and setters can be configured, including their names, whether they Copy and which error type E is used. See Field attributes.

Casting methods

The top-level enum has methods to cast it to each of the variants:

as_{variantname} returning Result<&{VariantStruct}, E>.
as_{variantname}_mut returning Result<&mut {VariantStruct}, E>.

The error type E may be controlled by the cast_error attribute.

Reference methods

The top-level enum has methods for converting it into the Ref and RefMut types, which are described here.

to_ref returning {BaseName}Ref.
to_mut returning {BaseName}RefMut.

`From` implementations

The top-level enum has From implementations for converting (owned) variant structs, i.e.

impl From<{VariantStruct}> for {BaseName} for all variants

Attributes on the enum variants

To add attributes to the enum variants, enum_variant_attributes and specific_enum_variant_attributes can be used.

Consider a variant of the MyStruct example where you want to derive serde::Serialize. However, one of the fields has a lifetime thus the #[serde(borrow)] attribute is required on the enum variants. In addition, you want to change the name of one of the enum variants when it’s serialized:

#![allow(unused)]
fn main() {
#[superstruct(
    variants(Foo, Bar),
    enum_variant_attributes(serde(borrow)),
    specific_enum_variant_attributes(Bar(serde(rename = "Baz"))),
)]
#[derive(serde::Serialize)]
struct MyStruct<'a> {
    name: &'a str,
    #[superstruct(only(Foo))]
    location: u16,
}
}