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".

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 otter_nodejs_tests::tera::Map<String, Value>

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

impl FromIterator<Weekday> for WeekdaySet

impl FromIterator<AsciiChar> for String

impl FromIterator<Signal> for SigSet

impl FromIterator<char> for Box<str>

impl FromIterator<char> for ByteString

impl FromIterator<char> for String

impl FromIterator<char> for BString

impl FromIterator<u8> for ByteString

impl FromIterator<u8> for BString

impl FromIterator<u8> for Bytes

impl FromIterator<u8> for BytesMut

impl FromIterator<()> for ()

impl FromIterator<AtFlags> for otter_nodejs_tests::nix::fcntl::AtFlags

impl FromIterator<FallocateFlags> for otter_nodejs_tests::nix::fcntl::FallocateFlags

impl FromIterator<FdFlag> for otter_nodejs_tests::nix::fcntl::FdFlag

impl FromIterator<OFlag> for OFlag

impl FromIterator<RenameFlags> for otter_nodejs_tests::nix::fcntl::RenameFlags

impl FromIterator<SealFlag> for SealFlag

impl FromIterator<SpliceFFlags> for SpliceFFlags

impl FromIterator<DeleteModuleFlags> for DeleteModuleFlags

impl FromIterator<ModuleInitFlags> for ModuleInitFlags

impl FromIterator<MntFlags> for MntFlags

impl FromIterator<MsFlags> for otter_nodejs_tests::nix::mount::MsFlags

impl FromIterator<FdFlag> for otter_nodejs_tests::nix::mqueue::FdFlag

impl FromIterator<MQ_OFlag> for MQ_OFlag

impl FromIterator<InterfaceFlags> for InterfaceFlags

impl FromIterator<PollFlags> for PollFlags

impl FromIterator<CloneFlags> for CloneFlags

impl FromIterator<EpollCreateFlags> for EpollCreateFlags

impl FromIterator<EpollFlags> for EpollFlags

impl FromIterator<EfdFlags> for EfdFlags

impl FromIterator<AddWatchFlags> for AddWatchFlags

impl FromIterator<InitFlags> for InitFlags

impl FromIterator<MemFdCreateFlag> for MemFdCreateFlag

impl FromIterator<MRemapFlags> for MRemapFlags

impl FromIterator<MapFlags> for MapFlags

impl FromIterator<MlockAllFlags> for MlockAllFlags

impl FromIterator<MsFlags> for otter_nodejs_tests::nix::sys::mman::MsFlags

impl FromIterator<ProtFlags> for ProtFlags

impl FromIterator<Persona> for Persona

impl FromIterator<Options> for Options

impl FromIterator<QuotaValidFlags> for QuotaValidFlags

impl FromIterator<SaFlags> for SaFlags

impl FromIterator<SfdFlags> for SfdFlags

impl FromIterator<MsgFlags> for MsgFlags

impl FromIterator<SockFlag> for SockFlag

impl FromIterator<TimestampingFlag> for TimestampingFlag

impl FromIterator<Mode> for otter_nodejs_tests::nix::sys::stat::Mode

impl FromIterator<SFlag> for SFlag

impl FromIterator<FsFlags> for FsFlags

impl FromIterator<ControlFlags> for ControlFlags

impl FromIterator<InputFlags> for InputFlags

impl FromIterator<LocalFlags> for LocalFlags

impl FromIterator<OutputFlags> for OutputFlags

impl FromIterator<TimerFlags> for TimerFlags

impl FromIterator<TimerSetTimeFlags> for TimerSetTimeFlags

impl FromIterator<WaitPidFlag> for WaitPidFlag

impl FromIterator<AccessFlags> for AccessFlags

impl FromIterator<ByteString> for ByteString

impl FromIterator<String> for Box<str>

impl FromIterator<String> for String

impl FromIterator<OsString> for OsString

impl FromIterator<BString> for BString

impl FromIterator<FileType> for FileType

impl FromIterator<EventMask> for EventMask

impl FromIterator<WatchMask> for WatchMask

impl FromIterator<Op> for Op

impl FromIterator<CipherCtxFlags> for CipherCtxFlags

impl FromIterator<CMSOptions> for CMSOptions

impl FromIterator<OcspFlag> for OcspFlag

Trait FromIterator

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

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

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, 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 futures_util::future::select_all::SelectAll<Fut>
where Fut: Future + Unpin,

impl<Fut> FromIterator<Fut> for SelectOk<Fut>
where Fut: TryFuture + Unpin,