Module scale_info::build

Expand description

Builders for defining metadata for variant types (enums), and composite types (structs). They are designed to allow only construction of valid definitions.

In most cases we recommend using the scale-info-derive crate to auto generate the builder constructions.

Examples

Generic struct

struct Foo<T> {
    bar: T,
    data: u64,
}

impl<T> TypeInfo for Foo<T>
where
    T: TypeInfo + 'static,
{
    type Identity = Self;

    fn type_info() -> Type {
        Type::builder()
            .path(Path::new("Foo", module_path!()))
            .type_params(type_params!(T))
            .composite(Fields::named()
                .field(|f| f.ty::<T>().name("bar").type_name("T"))
                .field(|f| f.ty::<u64>().name("data").type_name("u64"))
            )
    }
}

Tuple struct

struct Foo(u32, bool);

impl TypeInfo for Foo {
    type Identity = Self;

    fn type_info() -> Type {
        Type::builder()
            .path(Path::new("Foo", module_path!()))
            .composite(Fields::unnamed()
                .field(|f| f.ty::<u32>().type_name("u32"))
                .field(|f| f.ty::<bool>().type_name("bool"))
            )
    }
}

Enum with fields

enum Foo<T>{
    A(T),
    B { f: u32 },
    C,
}

impl<T> TypeInfo for Foo<T>
where
    T: TypeInfo + 'static,
{
    type Identity = Self;

    fn type_info() -> Type {
        Type::builder()
            .path(Path::new("Foo", module_path!()))
               .type_params(type_params!(T))
            .variant(
                Variants::new()
                    .variant("A", |v| v
                        .index(0)
                        .fields(Fields::unnamed().field(|f| f.ty::<T>().type_name("T")))
                    )
                    .variant("B", |v| v
                        .index(1)
                        .fields(Fields::named().field(|f| f.ty::<u32>().name("f").type_name("u32")))
                    )
                    .variant_unit("A", 2)
            )
    }
}

Enum without fields, aka C-style enums.

enum Foo {
    A,
    B,
    C = 33,
}

impl TypeInfo for Foo {
    type Identity = Self;

    fn type_info() -> Type {
        Type::builder()
            .path(Path::new("Foo", module_path!()))
            .variant(
                Variants::new()
                    .variant("A", |v| v.index(1))
                    .variant("B", |v| v.index(2))
                    .variant("C", |v| v.index(33))
            )
    }
}