Trait std::default::Default
[−]
[src]
pub trait Default {
fn default() -> Self;
}A trait for giving a type a useful default value.
A struct can derive default implementations of Default for basic types using
#[derive(Default)].
Examples
fn main() { #[allow(dead_code)] #[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() { #[allow(dead_code)] 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<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 E: Default, J: Default, L: Default, C: Default, F: Default, I: Default, A: Default, H: Default, G: Default, K: Default, D: Default, B: 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 E: Default, A: Default, D: Default, B: Default, J: Default, F: Default, K: Default, G: Default, C: Default, I: Default, H: Defaultimpl<A, B, C, D, E, F, G, H, I, J> Default for (A, B, C, D, E, F, G, H, I, J) where F: Default, H: Default, G: Default, D: Default, A: Default, B: Default, J: Default, C: Default, I: Default, E: Defaultimpl<A, B, C, D, E, F, G, H, I> Default for (A, B, C, D, E, F, G, H, I) where D: Default, A: Default, C: Default, F: Default, I: Default, E: Default, H: Default, G: Default, B: Defaultimpl<A, B, C, D, E, F, G, H> Default for (A, B, C, D, E, F, G, H) where D: Default, H: Default, E: Default, B: Default, F: Default, C: Default, G: Default, A: Defaultimpl<A, B, C, D, E, F, G> Default for (A, B, C, D, E, F, G) where B: Default, C: Default, A: Default, D: Default, F: Default, E: Default, G: Defaultimpl<A, B, C, D, E, F> Default for (A, B, C, D, E, F) where A: Default, C: Default, B: Default, E: Default, F: Default, D: Defaultimpl<A, B, C, D, E> Default for (A, B, C, D, E) where B: Default, C: Default, E: Default, D: Default, A: Defaultimpl<A, B, C, D> Default for (A, B, C, D) where C: Default, D: Default, B: Default, A: Defaultimpl<A, B, C> Default for (A, B, C) where B: Default, C: Default, A: Defaultimpl<A, B> Default for (A, B) where A: Default, B: Defaultimpl<A> Default for (A,) where A: Defaultimpl<'a> Default for &'a strimpl<'a, T> Default for &'a mut [T]impl<'a, T> Default for &'a [T]impl<T> Default for [T; 0]impl<T> Default for [T; 1] where T: Defaultimpl<T> Default for [T; 2] where T: Defaultimpl<T> Default for [T; 3] where T: Defaultimpl<T> Default for [T; 4] where T: Defaultimpl<T> Default for [T; 5] where T: Defaultimpl<T> Default for [T; 6] where T: Defaultimpl<T> Default for [T; 7] where T: Defaultimpl<T> Default for [T; 8] where T: Defaultimpl<T> Default for [T; 9] where T: Defaultimpl<T> Default for [T; 10] where T: Defaultimpl<T> Default for [T; 11] where T: Defaultimpl<T> Default for [T; 12] where T: Defaultimpl<T> Default for [T; 13] where T: Defaultimpl<T> Default for [T; 14] where T: Defaultimpl<T> Default for [T; 15] where T: Defaultimpl<T> Default for [T; 16] where T: Defaultimpl<T> Default for [T; 17] where T: Defaultimpl<T> Default for [T; 18] where T: Defaultimpl<T> Default for [T; 19] where T: Defaultimpl<T> Default for [T; 20] where T: Defaultimpl<T> Default for [T; 21] where T: Defaultimpl<T> Default for [T; 22] where T: Defaultimpl<T> Default for [T; 23] where T: Defaultimpl<T> Default for [T; 24] where T: Defaultimpl<T> Default for [T; 25] where T: Defaultimpl<T> Default for [T; 26] where T: Defaultimpl<T> Default for [T; 27] where T: Defaultimpl<T> Default for [T; 28] where T: Defaultimpl<T> Default for [T; 29] where T: Defaultimpl<T> Default for [T; 30] where T: Defaultimpl<T> Default for [T; 31] where T: Defaultimpl<T> Default for [T; 32] where T: Defaultimpl Default for f64impl Default for f32impl Default for i64impl Default for i32impl Default for i16impl Default for i8impl Default for isizeimpl Default for u64impl Default for u32impl Default for u16impl Default for u8impl Default for usizeimpl Default for charimpl Default for boolimpl Default for ()impl<T> Default for Cell<T> where T: Copy + Defaultimpl<T> Default for RefCell<T> where T: Defaultimpl<H> Default for BuildHasherDefault<H>impl Default for SipHasherimpl<T> Default for Empty<T>impl<T> Default for PhantomData<T> where T: ?Sizedimpl<T> Default for Option<T>impl<T> Default for Box<[T]>impl<T> Default for Box<T> where T: Defaultimpl<T> Default for Rc<T> where T: Defaultimpl Default for Stringimpl<T> Default for Vec<T>impl<T> Default for Wrapping<T> where T: Defaultimpl<T> Default for BinaryHeap<T> where T: Ordimpl<K, V> Default for BTreeMap<K, V> where K: Ordimpl<T> Default for BTreeSet<T> where T: Ordimpl<T> Default for LinkedList<T>impl<T> Default for VecDeque<T>impl<K, V, S> Default for HashMap<K, V, S> where K: Eq + Hash, S: BuildHasher + Defaultimpl Default for RandomStateimpl<T, S> Default for HashSet<T, S> where T: Eq + Hash, S: BuildHasher + Defaultimpl Default for OsStringimpl<'a> Default for &'a OsStrimpl<T> Default for Arc<T> where T: Defaultimpl Default for AtomicBoolimpl Default for AtomicIsizeimpl Default for AtomicUsizeimpl<T> Default for AtomicPtr<T>impl Default for ReseedWithDefault