Enum Fields

pub enum Fields {
    Named(FieldsNamed),
    Unnamed(FieldsUnnamed),
    Unit,
}

Available on crate features full or derive only.

Data stored within an enum variant or struct.

Syntax tree enum

This type is a syntax tree enum.

Variants

Named(FieldsNamed)

Named fields of a struct or struct variant such as Point { x: f64, y: f64 }.

Unnamed(FieldsUnnamed)

Unnamed fields of a tuple struct or tuple variant such as Some(T).

Unit

Unit struct or unit variant such as None.

Implementations

impl Fields

pub fn iter(&self) -> Iter<'_, Field>

Get an iterator over the borrowed Field items in this object. This iterator can be used to iterate over a named or unnamed struct or variant’s fields uniformly.

pub fn iter_mut(&mut self) -> IterMut<'_, Field>

Get an iterator over the mutably borrowed Field items in this object. This iterator can be used to iterate over a named or unnamed struct or variant’s fields uniformly.

pub fn len(&self) -> usize

Returns the number of fields.

pub fn is_empty(&self) -> bool

Returns true if there are zero fields.

pub fn members(&self) -> impl Iterator<Item = Member> + Clone + '_

Get an iterator over the fields of a struct or variant as Members. This iterator can be used to iterate over a named or unnamed struct or variant’s fields uniformly.

Example

The following is a simplistic Clone derive for structs. (A more complete implementation would additionally want to infer trait bounds on the generic type parameters.)

fn derive_clone(input: &syn::ItemStruct) -> proc_macro2::TokenStream {
    let ident = &input.ident;
    let members = input.fields.members();
    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
    quote! {
        impl #impl_generics Clone for #ident #ty_generics #where_clause {
            fn clone(&self) -> Self {
                Self {
                    #(#members: self.#members.clone()),*
                }
            }
        }
    }
}

For structs with named fields, it produces an expression like Self { a: self.a.clone() }. For structs with unnamed fields, Self { 0: self.0.clone() }. And for unit structs, Self {}.

Trait Implementations

impl Clone for Fields

Available on crate feature clone-impls only.

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Fields

Available on crate feature extra-traits only.

fn fmt(&self, formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl From<FieldsNamed> for Fields

fn from(e: FieldsNamed) -> Fields

Converts to this type from the input type.

impl From<FieldsUnnamed> for Fields

fn from(e: FieldsUnnamed) -> Fields

Converts to this type from the input type.

impl Hash for Fields

Available on crate feature extra-traits only.

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'a> IntoIterator for &'a Fields

type Item = &'a Field

The type of the elements being iterated over.

type IntoIter = Iter<'a, Field>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a> IntoIterator for &'a mut Fields

type Item = &'a mut Field

The type of the elements being iterated over.

type IntoIter = IterMut<'a, Field>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl IntoIterator for Fields

type Item = Field

The type of the elements being iterated over.

type IntoIter = IntoIter<Field>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl PartialEq for Fields

Available on crate feature extra-traits only.

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl ToTokens for Fields

Available on crate feature printing only.

fn to_tokens(&self, tokens: &mut TokenStream)

Write self to the given TokenStream.

fn to_token_stream(&self) -> TokenStream

Convert self directly into a TokenStream object.

fn into_token_stream(self) -> TokenStream

where Self: Sized,

Convert self directly into a TokenStream object.

impl Eq for Fields

Available on crate feature extra-traits only.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 56 bytes

Size for each variant:

• Named: 48 bytes
• Unnamed: 48 bytes
• Unit: 0 bytes