Module scale_info::build

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))
            )
    }
}

Modules

• field_state
  Type states for building a field.
• state
  State types for type builders which require a Path.
• variant_state
  State types for the VariantBuilder which requires an index.

Structs

• FieldBuilder
  Construct a valid Field.
• Fields
  Provides FieldsBuilder constructors
• FieldsBuilder
  Build a set of either all named (e.g. for a struct) or all unnamed (e.g. for a tuple struct)
• TypeBuilder
  Builds a Type
• VariantBuilder
  Build a Variant.
• Variants
  Builds a definition of a variant type i.e an enum

Enums

• NamedFields
  A fields builder only allows named fields (e.g. a struct)
• NoFields
  A fields builder has no fields (e.g. a unit struct)
• UnnamedFields
  A fields builder only allows unnamed fields (e.g. a tuple)