Trait ExtendWithCapacity

pub trait ExtendWithCapacity<T>: Extend<T> {
    // Required method
    fn with_capacity(capacity: usize) -> Self;
}

A trait for collections that can be pre-allocated with specific capacity and extended with elements.

This extends the standard Extend trait to provide a uniform interface for collection types that support capacity pre-allocation.

Pre-allocating capacity can improve performance when the number of elements is known in advance. Due to the fact that in Rust iterators, size_hint() might return (0, None), pre-allocating capacity can be particularly useful.

Implementors

• alloc collections: Vec<T>, String, VecDeque<T>, BinaryHeap<T>
• std types (with std feature): OsString, HashMap, HashSet, PathBuf
• AHash collections (with ahash & std features): AHashMap, AHashSet

Required Methods

fn with_capacity(capacity: usize) -> Self

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<K, S> ExtendWithCapacity<K> for HashSet<K, S>

where K: Eq + Hash, S: BuildHasher + Default,

Available on crate feature std only.

fn with_capacity(capacity: usize) -> Self

impl<K, S> ExtendWithCapacity<K> for IndexSet<K, S>

where K: Eq + Hash, S: BuildHasher + Default,

Available on crate feature indexmap only.

fn with_capacity(capacity: usize) -> Self

impl<K, V, S> ExtendWithCapacity<(K, V)> for HashMap<K, V, S>

where K: Eq + Hash, S: BuildHasher + Default,

Available on crate feature std only.

fn with_capacity(capacity: usize) -> Self

impl<K, V, S> ExtendWithCapacity<(K, V)> for IndexMap<K, V, S>

where K: Eq + Hash, S: BuildHasher + Default,

Available on crate feature indexmap only.

fn with_capacity(capacity: usize) -> Self

impl<K: Eq + Hash> ExtendWithCapacity<K> for AHashSet<K>

Available on crate feature ahash only.

fn with_capacity(capacity: usize) -> Self

impl<K: Eq + Hash, V> ExtendWithCapacity<(K, V)> for AHashMap<K, V>

Available on crate feature ahash only.

fn with_capacity(capacity: usize) -> Self

impl<T> ExtendWithCapacity<T> for VecDeque<T>

fn with_capacity(capacity: usize) -> Self

impl<T> ExtendWithCapacity<T> for String

where String: Extend<T>,

fn with_capacity(capacity: usize) -> Self

impl<T> ExtendWithCapacity<T> for Vec<T>

fn with_capacity(capacity: usize) -> Self

impl<T> ExtendWithCapacity<T> for OsString

where OsString: Extend<T>,

Available on crate feature std only.

fn with_capacity(capacity: usize) -> Self

impl<T: Ord> ExtendWithCapacity<T> for BinaryHeap<T>

fn with_capacity(capacity: usize) -> Self

impl<T: AsRef<Path>> ExtendWithCapacity<T> for PathBuf

Available on crate feature std only.

fn with_capacity(capacity: usize) -> Self

Implementors