pub trait Extend<A> {
fn extend<T>(&mut self, iter: T)
where
T: IntoIterator<Item = A>;
fn extend_one(&mut self, item: A) { ... }
fn extend_reserve(&mut self, additional: usize) { ... }
}
Expand description
Extend a collection with the contents of an iterator.
Iterators produce a series of values, and collections can also be thought
of as a series of values. The Extend
trait bridges this gap, allowing you
to extend a collection by including the contents of that iterator. When
extending a collection with an already existing key, that entry is updated
or, in the case of collections that permit multiple entries with equal
keys, that entry is inserted.
Examples
Basic usage:
// You can extend a String with some chars:
let mut message = String::from("The first three letters are: ");
message.extend(&['a', 'b', 'c']);
assert_eq!("abc", &message[29..32]);
Implementing Extend
:
// A sample collection, that's just a wrapper over Vec<T>
#[derive(Debug)]
struct MyCollection(Vec<i32>);
// Let's give it some methods so we can create one and add things
// to it.
impl MyCollection {
fn new() -> MyCollection {
MyCollection(Vec::new())
}
fn add(&mut self, elem: i32) {
self.0.push(elem);
}
}
// since MyCollection has a list of i32s, we implement Extend for i32
impl Extend<i32> for MyCollection {
// This is a bit simpler with the concrete type signature: we can call
// extend on anything which can be turned into an Iterator which gives
// us i32s. Because we need i32s to put into MyCollection.
fn extend<T: IntoIterator<Item=i32>>(&mut self, iter: T) {
// The implementation is very straightforward: loop through the
// iterator, and add() each element to ourselves.
for elem in iter {
self.add(elem);
}
}
}
let mut c = MyCollection::new();
c.add(5);
c.add(6);
c.add(7);
// let's extend our collection with three more numbers
c.extend(vec![1, 2, 3]);
// we've added these elements onto the end
assert_eq!("MyCollection([5, 6, 7, 1, 2, 3])", format!("{c:?}"));
Required methods
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = A>,
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = A>,
Extends a collection with the contents of an iterator.
As this is the only required method for this trait, the trait-level docs contain more details.
Examples
Basic usage:
// You can extend a String with some chars:
let mut message = String::from("abc");
message.extend(['d', 'e', 'f'].iter());
assert_eq!("abcdef", &message);
Provided methods
fn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one
)Extends a collection with exactly one element.
fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)Reserves capacity in a collection for the given number of additional elements.
The default implementation does nothing.
Implementations on Foreign Types
1.52.0 · sourceimpl<'a> Extend<&'a OsStr> for OsString
impl<'a> Extend<&'a OsStr> for OsString
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = &'a OsStr>,
sourceimpl<K, V, S> Extend<(K, V)> for HashMap<K, V, S> where
K: Eq + Hash,
S: BuildHasher,
impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S> where
K: Eq + Hash,
S: BuildHasher,
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = (K, V)>,
sourcefn extend_one(&mut self, (K, V))
fn extend_one(&mut self, (K, V))
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.4.0 · sourceimpl<'a, T, S> Extend<&'a T> for HashSet<T, S> where
T: 'a + Eq + Hash + Copy,
S: BuildHasher,
impl<'a, T, S> Extend<&'a T> for HashSet<T, S> where
T: 'a + Eq + Hash + Copy,
S: BuildHasher,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
sourcefn extend_one(&mut self, &'a T)
fn extend_one(&mut self, &'a T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.52.0 · sourceimpl Extend<OsString> for OsString
impl Extend<OsString> for OsString
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = OsString>,
sourceimpl<P> Extend<P> for PathBuf where
P: AsRef<Path>,
impl<P> Extend<P> for PathBuf where
P: AsRef<Path>,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = P>,
sourcefn extend_one(&mut self, p: P)
fn extend_one(&mut self, p: P)
extend_one
)1.4.0 · sourceimpl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S> where
K: Eq + Hash + Copy,
V: Copy,
S: BuildHasher,
impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S> where
K: Eq + Hash + Copy,
V: Copy,
S: BuildHasher,
sourceimpl<T, S> Extend<T> for HashSet<T, S> where
T: Eq + Hash,
S: BuildHasher,
impl<T, S> Extend<T> for HashSet<T, S> where
T: Eq + Hash,
S: BuildHasher,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
sourcefn extend_one(&mut self, item: T)
fn extend_one(&mut self, item: T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.52.0 · sourceimpl<'a> Extend<Cow<'a, OsStr>> for OsString
impl<'a> Extend<Cow<'a, OsStr>> for OsString
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = Cow<'a, OsStr>>,
1.56.0 · sourceimpl<A, B, ExtendA, ExtendB> Extend<(A, B)> for (ExtendA, ExtendB) where
ExtendA: Extend<A>,
ExtendB: Extend<B>,
impl<A, B, ExtendA, ExtendB> Extend<(A, B)> for (ExtendA, ExtendB) where
ExtendA: Extend<A>,
ExtendB: Extend<B>,
sourcefn extend<T>(&mut self, into_iter: T) where
T: IntoIterator<Item = (A, B)>,
fn extend<T>(&mut self, into_iter: T) where
T: IntoIterator<Item = (A, B)>,
Allows to extend
a tuple of collections that also implement Extend
.
See also: Iterator::unzip
Examples
let mut tuple = (vec![0], vec![1]);
tuple.extend([(2, 3), (4, 5), (6, 7)]);
assert_eq!(tuple.0, [0, 2, 4, 6]);
assert_eq!(tuple.1, [1, 3, 5, 7]);
// also allows for arbitrarily nested tuples as elements
let mut nested_tuple = (vec![1], (vec![2], vec![3]));
nested_tuple.extend([(4, (5, 6)), (7, (8, 9))]);
let (a, (b, c)) = nested_tuple;
assert_eq!(a, [1, 4, 7]);
assert_eq!(b, [2, 5, 8]);
assert_eq!(c, [3, 6, 9]);
sourcefn extend_one(&mut self, item: (A, B))
fn extend_one(&mut self, item: (A, B))
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.28.0 · sourceimpl Extend<()> for ()
impl Extend<()> for ()
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = ()>,
sourcefn extend_one(&mut self, _item: ())
fn extend_one(&mut self, _item: ())
extend_one
)sourceimpl<'a> Extend<&'a str> for String
impl<'a> Extend<&'a str> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a str>,
sourcefn extend_one(&mut self, s: &'a str)
fn extend_one(&mut self, s: &'a str)
extend_one
)sourceimpl<T, A> Extend<T> for VecDeque<T, A> where
A: Allocator,
impl<T, A> Extend<T> for VecDeque<T, A> where
A: Allocator,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
sourcefn extend_one(&mut self, elem: T)
fn extend_one(&mut self, elem: T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.2.0 · sourceimpl<'a, T, A> Extend<&'a T> for Vec<T, A> where
T: 'a + Copy,
A: 'a + Allocator,
impl<'a, T, A> Extend<&'a T> for Vec<T, A> where
T: 'a + Copy,
A: 'a + Allocator,
Extend implementation that copies elements out of references before pushing them onto the Vec.
This implementation is specialized for slice iterators, where it uses copy_from_slice
to
append the entire slice at once.
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
sourcefn extend_one(&mut self, &'a T)
fn extend_one(&mut self, &'a T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)sourceimpl<T> Extend<T> for BTreeSet<T> where
T: Ord,
impl<T> Extend<T> for BTreeSet<T> where
T: Ord,
fn extend<Iter>(&mut self, iter: Iter) where
Iter: IntoIterator<Item = T>,
sourcefn extend_one(&mut self, elem: T)
fn extend_one(&mut self, elem: T)
extend_one
)1.19.0 · sourceimpl<'a> Extend<Cow<'a, str>> for String
impl<'a> Extend<Cow<'a, str>> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = Cow<'a, str>>,
sourcefn extend_one(&mut self, s: Cow<'a, str>)
fn extend_one(&mut self, s: Cow<'a, str>)
extend_one
)1.2.0 · sourceimpl<'a> Extend<&'a char> for String
impl<'a> Extend<&'a char> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a char>,
sourcefn extend_one(&mut self, &'a char)
fn extend_one(&mut self, &'a char)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.4.0 · sourceimpl Extend<String> for String
impl Extend<String> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = String>,
sourcefn extend_one(&mut self, s: String)
fn extend_one(&mut self, s: String)
extend_one
)sourceimpl<T> Extend<T> for LinkedList<T>
impl<T> Extend<T> for LinkedList<T>
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
sourcefn extend_one(&mut self, elem: T)
fn extend_one(&mut self, elem: T)
extend_one
)sourceimpl<T> Extend<T> for BinaryHeap<T> where
T: Ord,
impl<T> Extend<T> for BinaryHeap<T> where
T: Ord,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
sourcefn extend_one(&mut self, item: T)
fn extend_one(&mut self, item: T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.2.0 · sourceimpl<'a, T, A> Extend<&'a T> for VecDeque<T, A> where
T: 'a + Copy,
A: Allocator,
impl<'a, T, A> Extend<&'a T> for VecDeque<T, A> where
T: 'a + Copy,
A: Allocator,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
sourcefn extend_one(&mut self, &T)
fn extend_one(&mut self, &T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)sourceimpl<T, A> Extend<T> for Vec<T, A> where
A: Allocator,
impl<T, A> Extend<T> for Vec<T, A> where
A: Allocator,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
sourcefn extend_one(&mut self, item: T)
fn extend_one(&mut self, item: T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.2.0 · sourceimpl<'a, K, V> Extend<(&'a K, &'a V)> for BTreeMap<K, V> where
K: Ord + Copy,
V: Copy,
impl<'a, K, V> Extend<(&'a K, &'a V)> for BTreeMap<K, V> where
K: Ord + Copy,
V: Copy,
1.2.0 · sourceimpl<'a, T> Extend<&'a T> for BTreeSet<T> where
T: 'a + Ord + Copy,
impl<'a, T> Extend<&'a T> for BTreeSet<T> where
T: 'a + Ord + Copy,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
sourcefn extend_one(&mut self, &'a T)
fn extend_one(&mut self, &'a T)
extend_one
)1.2.0 · sourceimpl<'a, T> Extend<&'a T> for LinkedList<T> where
T: 'a + Copy,
impl<'a, T> Extend<&'a T> for LinkedList<T> where
T: 'a + Copy,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
sourcefn extend_one(&mut self, &'a T)
fn extend_one(&mut self, &'a T)
extend_one
)sourceimpl Extend<char> for String
impl Extend<char> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = char>,
sourcefn extend_one(&mut self, c: char)
fn extend_one(&mut self, c: char)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)1.2.0 · sourceimpl<'a, T> Extend<&'a T> for BinaryHeap<T> where
T: 'a + Ord + Copy,
impl<'a, T> Extend<&'a T> for BinaryHeap<T> where
T: 'a + Ord + Copy,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
sourcefn extend_one(&mut self, &'a T)
fn extend_one(&mut self, &'a T)
extend_one
)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)sourceimpl<K, V> Extend<(K, V)> for BTreeMap<K, V> where
K: Ord,
impl<K, V> Extend<(K, V)> for BTreeMap<K, V> where
K: Ord,
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = (K, V)>,
sourcefn extend_one(&mut self, (K, V))
fn extend_one(&mut self, (K, V))
extend_one
)sourceimpl<K, V, S> Extend<(K, V)> for IndexMap<K, V, S> where
K: Hash + Eq,
S: BuildHasher,
impl<K, V, S> Extend<(K, V)> for IndexMap<K, V, S> where
K: Hash + Eq,
S: BuildHasher,
sourcefn extend<I>(&mut self, iterable: I) where
I: IntoIterator<Item = (K, V)>,
fn extend<I>(&mut self, iterable: I) where
I: IntoIterator<Item = (K, V)>,
Extend the map with all key-value pairs in the iterable.
This is equivalent to calling insert
for each of
them in order, which means that for keys that already existed
in the map, their value is updated but it keeps the existing order.
New keys are inserted in the order they appear in the sequence. If equivalents of a key occur more than once, the last corresponding value prevails.
sourceimpl<T, S> Extend<T> for IndexSet<T, S> where
T: Hash + Eq,
S: BuildHasher,
impl<T, S> Extend<T> for IndexSet<T, S> where
T: Hash + Eq,
S: BuildHasher,
fn extend<I>(&mut self, iterable: I) where
I: IntoIterator<Item = T>,
sourceimpl<'a, K, V, S> Extend<(&'a K, &'a V)> for IndexMap<K, V, S> where
K: Hash + Eq + Copy,
V: Copy,
S: BuildHasher,
impl<'a, K, V, S> Extend<(&'a K, &'a V)> for IndexMap<K, V, S> where
K: Hash + Eq + Copy,
V: Copy,
S: BuildHasher,
sourceimpl<'a, T, S> Extend<&'a T> for IndexSet<T, S> where
T: 'a + Hash + Eq + Copy,
S: BuildHasher,
impl<'a, T, S> Extend<&'a T> for IndexSet<T, S> where
T: 'a + Hash + Eq + Copy,
S: BuildHasher,
fn extend<I>(&mut self, iterable: I) where
I: IntoIterator<Item = &'a T>,
sourceimpl<T, S, A> Extend<T> for HashSet<T, S, A> where
T: Eq + Hash,
S: BuildHasher,
A: Allocator + Clone,
impl<T, S, A> Extend<T> for HashSet<T, S, A> where
T: Eq + Hash,
S: BuildHasher,
A: Allocator + Clone,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
sourceimpl<K, V, S, A> Extend<(K, V)> for HashMap<K, V, S, A> where
K: Eq + Hash,
S: BuildHasher,
A: Allocator + Clone,
impl<K, V, S, A> Extend<(K, V)> for HashMap<K, V, S, A> where
K: Eq + Hash,
S: BuildHasher,
A: Allocator + Clone,
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.