rustmax::cxx_build::std::prelude::rust_2024

Trait FromIterator

1.85.0 · 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.

Trait FromIteratorCopy item path

§Examples

Required Methods§

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

§Examples

Dyn Compatibility§

Implementors§

impl FromIterator<(Key, Value)> for Fields

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

impl FromIterator<Signal> for nix::sys::signal::SigSet

impl FromIterator<Signal> for nix::sys::signal::SigSet

impl FromIterator<TokenTree> for rustmax::proc_macro2::TokenStream

impl FromIterator<TokenTree> for rustmax::proc_macro::TokenStream

impl FromIterator<char> for BString

impl FromIterator<char> for ByteString

impl FromIterator<char> for Box<str>

impl FromIterator<char> for String

impl FromIterator<u8> for BString

impl FromIterator<u8> for ByteString

impl FromIterator<u8> for Bytes

impl FromIterator<u8> for BytesMut

impl FromIterator<()> for ()

impl FromIterator<usize> for VarBitSet

impl FromIterator<BString> for BString

impl FromIterator<FileType> for FileType

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

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

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

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

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

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

impl FromIterator<OFlag> for nix::fcntl::OFlag

impl FromIterator<OFlag> for nix::fcntl::OFlag

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

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

impl FromIterator<ResolveFlag> for nix::fcntl::ResolveFlag

impl FromIterator<ResolveFlag> for nix::fcntl::ResolveFlag

impl FromIterator<SealFlag> for nix::fcntl::SealFlag

impl FromIterator<SealFlag> for nix::fcntl::SealFlag

impl FromIterator<PollFlags> for PollFlags

impl FromIterator<PosixSpawnFlags> for PosixSpawnFlags

impl FromIterator<MFdFlags> for MFdFlags

impl FromIterator<MemFdCreateFlag> for MemFdCreateFlag

impl FromIterator<SaFlags> for nix::sys::signal::SaFlags

impl FromIterator<SaFlags> for nix::sys::signal::SaFlags

impl FromIterator<SfdFlags> for nix::sys::signalfd::SfdFlags

impl FromIterator<SfdFlags> for nix::sys::signalfd::SfdFlags

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

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

impl FromIterator<SFlag> for nix::sys::stat::SFlag

impl FromIterator<SFlag> for nix::sys::stat::SFlag

impl FromIterator<FsFlags> for nix::sys::statvfs::FsFlags

impl FromIterator<FsFlags> for nix::sys::statvfs::FsFlags

impl FromIterator<ControlFlags> for ControlFlags

impl FromIterator<InputFlags> for InputFlags

impl FromIterator<LocalFlags> for LocalFlags

impl FromIterator<OutputFlags> for OutputFlags

impl FromIterator<WaitPidFlag> for nix::sys::wait::WaitPidFlag

impl FromIterator<WaitPidFlag> for nix::sys::wait::WaitPidFlag

impl FromIterator<AccessFlags> for nix::unistd::AccessFlags

impl FromIterator<AccessFlags> for nix::unistd::AccessFlags

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::fs::inotify::CreateFlags

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

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

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

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

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

Trait FromIterator

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