Trait FromIterator

1.0.0 · Source

pub trait FromIterator<A>: Sized {
    // Required method
    fn from_iter<T>(iter: T) -> Self
       where T: IntoIterator<Item = A>;
}

Expand description

Conversion from an Iterator.

By implementing FromIterator for a type, you define how it will be created from an iterator. This is common for types which describe a collection of some kind.

If you want to create a collection from the contents of an iterator, the Iterator::collect() method is preferred. However, when you need to specify the container type, FromIterator::from_iter() can be more readable than using a turbofish (e.g. ::<Vec<_>>()). See the Iterator::collect() documentation for more examples of its use.

§Examples

Basic usage:

let five_fives = std::iter::repeat(5).take(5);

let v = Vec::from_iter(five_fives);

assert_eq!(v, vec![5, 5, 5, 5, 5]);

Using Iterator::collect() to implicitly use FromIterator:

let five_fives = std::iter::repeat(5).take(5);

let v: Vec<i32> = five_fives.collect();

assert_eq!(v, vec![5, 5, 5, 5, 5]);

Using FromIterator::from_iter() as a more readable alternative to Iterator::collect():

use std::collections::VecDeque;
let first = (0..10).collect::<VecDeque<i32>>();
let second = VecDeque::from_iter(0..10);

assert_eq!(first, second);

Implementing FromIterator for your type:

// 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);
    }
}

// and we'll implement FromIterator
impl FromIterator<i32> for MyCollection {
    fn from_iter<I: IntoIterator<Item=i32>>(iter: I) -> Self {
        let mut c = MyCollection::new();

        for i in iter {
            c.add(i);
        }

        c
    }
}

// Now we can make a new iterator...
let iter = (0..5).into_iter();

// ... and make a MyCollection out of it
let c = MyCollection::from_iter(iter);

assert_eq!(c.0, vec![0, 1, 2, 3, 4]);

// collect works too!

let iter = (0..5).into_iter();
let c: MyCollection = iter.collect();

assert_eq!(c.0, vec![0, 1, 2, 3, 4]);

Required Methods§

1.0.0 · Source

fn from_iter<T>(iter: T) -> Self
where T: IntoIterator<Item = A>,

Creates a value from an iterator.

See the module-level documentation for more.

§Examples

let five_fives = std::iter::repeat(5).take(5);

let v = Vec::from_iter(five_fives);

assert_eq!(v, vec![5, 5, 5, 5, 5]);

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.

FromIterator

Trait FromIterator Copy item path

§Examples

Required Methods§

fn from_iter<T>(iter: T) -> Selfwhere T: IntoIterator<Item = A>,

§Examples

Dyn Compatibility§

Implementors§

impl FromIterator<(String, Value)> for serde_json::map::Map<String, Value>

impl FromIterator<(String, Value)> for toml::map::Map<String, Value>

impl FromIterator<(String, String)> for OptionsMap

impl FromIterator<Error> for Option<Error>

impl FromIterator<RelayId> for RelayIdSet

impl FromIterator<RelayFamilyId> for RelayFamilyIds

impl FromIterator<AsciiChar> for String

impl FromIterator<char> for BString

impl FromIterator<char> for Box<str>

impl FromIterator<char> for ByteString

impl FromIterator<char> for String

impl FromIterator<u8> for BString

impl FromIterator<u8> for Bytes

impl FromIterator<u8> for BytesMut

impl FromIterator<u8> for B64

impl FromIterator<u8> for ByteString

impl FromIterator<()> for ()

impl FromIterator<BString> for BString

impl FromIterator<EventMask> for EventMask

impl FromIterator<WatchMask> for WatchMask

impl FromIterator<EventKindMask> for EventKindMask

impl FromIterator<CipherCtxFlags> for CipherCtxFlags

impl FromIterator<CMSOptions> for CMSOptions

impl FromIterator<OcspFlag> for OcspFlag

impl FromIterator<Pkcs7Flags> for Pkcs7Flags

impl FromIterator<ExtensionContext> for ExtensionContext

impl FromIterator<ShutdownState> for ShutdownState

impl FromIterator<SslMode> for SslMode

impl FromIterator<SslOptions> for SslOptions

impl FromIterator<SslSessionCacheMode> for SslSessionCacheMode

impl FromIterator<SslVerifyMode> for SslVerifyMode

impl FromIterator<X509CheckFlags> for X509CheckFlags

impl FromIterator<X509VerifyFlags> for X509VerifyFlags

impl FromIterator<Literal> for Seq

impl FromIterator<CreateFlags> for rustix::backend::event::epoll::CreateFlags

impl FromIterator<EventFlags> for EventFlags

impl FromIterator<PollFlags> for PollFlags

impl FromIterator<EventfdFlags> for EventfdFlags

impl FromIterator<CreateFlags> for rustix::backend::fs::inotify::CreateFlags

impl FromIterator<ReadFlags> for ReadFlags

impl FromIterator<WatchFlags> for WatchFlags

impl FromIterator<Access> for Access

impl FromIterator<AtFlags> for AtFlags

impl FromIterator<FallocateFlags> for FallocateFlags

impl FromIterator<MemfdFlags> for MemfdFlags

impl FromIterator<Mode> for Mode

impl FromIterator<OFlags> for OFlags

impl FromIterator<RenameFlags> for RenameFlags

impl FromIterator<ResolveFlags> for ResolveFlags

impl FromIterator<SealFlags> for SealFlags

impl FromIterator<StatVfsMountFlags> for StatVfsMountFlags

impl FromIterator<DupFlags> for DupFlags

impl FromIterator<FdFlags> for FdFlags

impl FromIterator<ReadWriteFlags> for ReadWriteFlags

impl FromIterator<RecvFlags> for RecvFlags

impl FromIterator<ReturnFlags> for ReturnFlags

impl FromIterator<SendFlags> for SendFlags

impl FromIterator<PipeFlags> for PipeFlags

impl FromIterator<SpliceFlags> for SpliceFlags

impl FromIterator<TimerfdFlags> for TimerfdFlags

impl FromIterator<TimerfdTimerFlags> for TimerfdTimerFlags

impl FromIterator<IFlags> for IFlags

impl FromIterator<StatxAttributes> for StatxAttributes

impl FromIterator<StatxFlags> for StatxFlags

impl FromIterator<XattrFlags> for XattrFlags

impl FromIterator<SocketFlags> for SocketFlags

impl FromIterator<TxTimeFlags> for TxTimeFlags

impl FromIterator<SocketAddrXdpFlags> for SocketAddrXdpFlags

impl FromIterator<XdpDescOptions> for XdpDescOptions

impl FromIterator<XdpOptionsFlags> for XdpOptionsFlags

impl FromIterator<XdpRingFlags> for XdpRingFlags

impl FromIterator<XdpUmemRegFlags> for XdpUmemRegFlags

Trait FromIterator

fn from_iter<T>(iter: T) -> Self
where T: IntoIterator<Item = A>,

impl<'a, A, B, C, K0, K1, V> FromIterator<(A, B, C)> for ZeroMap2d<'a, K0, K1, V>
where A: Borrow<K0>, B: Borrow<K1>, C: Borrow<V>, K0: ZeroMapKV<'a> + Ord + ?Sized, K1: ZeroMapKV<'a> + Ord + ?Sized, V: ZeroMapKV<'a> + ?Sized,

impl<'a, A, B, K, V> FromIterator<(A, B)> for ZeroMap<'a, K, V>
where A: Borrow<K>, B: Borrow<V>, K: ZeroMapKV<'a> + Ord + ?Sized, V: ZeroMapKV<'a> + ?Sized,

impl<'a, M, T1, T2, O1, O2> FromIterator<BitRef<'a, M, T2, O2>> for BitVec<T1, O1>
where M: Mutability, T1: BitStore, T2: BitStore, O1: BitOrder, O2: BitOrder,

impl<'a, T> FromIterator<T> for Cow<'a, [T]>
where T: Clone,

impl<'a, T, O> FromIterator<&'a bool> for BitVec<T, O>
where T: BitStore, O: BitOrder,

impl<'a, T, O> FromIterator<&'a T> for BitVec<T, O>
where T: BitStore, O: BitOrder,

impl<A> FromIterator<<A as Array>::Item> for SmallVec<A>
where A: Array,

impl<A> FromIterator<Box<str, A>> for Box<str>
where A: Allocator,

impl<A> FromIterator<Box<str, A>> for String
where A: Allocator,

impl<A> FromIterator<A> for AsciiString
where A: AsRef<AsciiStr>,

impl<A> FromIterator<A> for SubprotocolRequest
where A: Into<NumberedSubver>,

impl<A, E, V> FromIterator<Result<A, E>> for Result<V, E>
where V: FromIterator<A>,

impl<A, V> FromIterator<Option<A>> for Option<V>
where V: FromIterator<A>,

impl<F> FromIterator<F> for JoinAll<F>
where F: Future,

impl<F> FromIterator<F> for TryJoinAll<F>
where F: TryFuture,

impl<Fut> FromIterator<Fut> for FuturesOrdered<Fut>
where Fut: Future,