Trait std::default::Default
[−]
[src]
pub trait Default {
fn default() -> Self;
}A trait that types which have a useful default value should implement.
A struct can derive default implementations of Default`Defaultfor basic types using` for basic types using
#[derive(Default)]`#[derive(Default)]`.
Examples
fn main() { #[derive(Default)] struct SomeOptions { foo: i32, bar: f32, } }#[derive(Default)] struct SomeOptions { foo: i32, bar: f32, }
Required Methods
fn default() -> Self
Returns the "default value" for a type.
Default values are often some kind of initial value, identity value, or anything else that may make sense as a default.
Examples
Using built-in default values:
fn main() { let i: i8 = Default::default(); let (x, y): (Option<String>, f64) = Default::default(); let (a, b, (c, d)): (i32, u32, (bool, bool)) = Default::default(); }let i: i8 = Default::default(); let (x, y): (Option<String>, f64) = Default::default(); let (a, b, (c, d)): (i32, u32, (bool, bool)) = Default::default();
Making your own:
fn main() { enum Kind { A, B, C, } impl Default for Kind { fn default() -> Kind { Kind::A } } }enum Kind { A, B, C, } impl Default for Kind { fn default() -> Kind { Kind::A } }
Implementors
impl Default for ()impl Default for boolimpl Default for charimpl Default for usizeimpl Default for u8impl Default for u16impl Default for u32impl Default for u64impl Default for isizeimpl Default for i8impl Default for i16impl Default for i32impl Default for i64impl Default for f32impl Default for f64impl Default for AtomicBoolimpl Default for AtomicIsizeimpl Default for AtomicUsizeimpl<T> Default for AtomicPtr<T>impl<T> Default for Cell<T> where T: Copy + Defaultimpl<T> Default for RefCell<T> where T: Defaultimpl<T> Default for Option<T>impl<'a, T> Default for &'a [T]impl<'a> Default for &'a strimpl Default for SipHasherimpl<A> Default for (A,) where A: Defaultimpl<A, B> Default for (A, B) where B: Default, A: Defaultimpl<A, B, C> Default for (A, B, C) where A: Default, B: Default, C: Defaultimpl<A, B, C, D> Default for (A, B, C, D) where A: Default, C: Default, D: Default, B: Defaultimpl<A, B, C, D, E> Default for (A, B, C, D, E) where C: Default, A: Default, E: Default, B: Default, D: Defaultimpl<A, B, C, D, E, F> Default for (A, B, C, D, E, F) where E: Default, F: Default, D: Default, B: Default, C: Default, A: Defaultimpl<A, B, C, D, E, F, G> Default for (A, B, C, D, E, F, G) where G: Default, F: Default, E: Default, C: Default, B: Default, A: Default, D: Defaultimpl<A, B, C, D, E, F, G, H> Default for (A, B, C, D, E, F, G, H) where E: Default, C: Default, F: Default, G: Default, D: Default, B: Default, A: Default, H: Defaultimpl<A, B, C, D, E, F, G, H, I> Default for (A, B, C, D, E, F, G, H, I) where I: Default, G: Default, E: Default, F: Default, H: Default, D: Default, B: Default, A: Default, C: Defaultimpl<A, B, C, D, E, F, G, H, I, J> Default for (A, B, C, D, E, F, G, H, I, J) where G: Default, J: Default, D: Default, A: Default, E: Default, B: Default, H: Default, C: Default, F: Default, I: Defaultimpl<A, B, C, D, E, F, G, H, I, J, K> Default for (A, B, C, D, E, F, G, H, I, J, K) where A: Default, H: Default, B: Default, G: Default, E: Default, D: Default, F: Default, I: Default, C: Default, K: Default, J: Defaultimpl<A, B, C, D, E, F, G, H, I, J, K, L> Default for (A, B, C, D, E, F, G, H, I, J, K, L) where G: Default, C: Default, H: Default, J: Default, B: Default, F: Default, A: Default, D: Default, K: Default, I: Default, E: Default, L: Defaultimpl<T> Default for Box<T> where T: Defaultimpl<T> Default for Box<[T]>impl<T> Default for Arc<T> where T: Defaultimpl<T> Default for Rc<T> where T: Defaultimpl<T> Default for BinaryHeap<T> where T: Ordimpl Default for BitVecimpl Default for BitSetimpl<K, V> Default for BTreeMap<K, V> where K: Ordimpl<T> Default for BTreeSet<T> where T: Ordimpl<T> Default for LinkedList<T>impl Default for Stringimpl<T> Default for Vec<T>impl<T> Default for VecDeque<T>impl<V> Default for VecMap<V>impl<K, V, S> Default for HashMap<K, V, S> where K: Eq + Hash, S: HashState + Defaultimpl Default for RandomStateimpl<T, S> Default for HashSet<T, S> where T: Eq + Hash, S: HashState + Defaultimpl<H> Default for DefaultState<H>impl Default for ReseedWithDefault