Struct ChainMap

pub struct ChainMap<K, V, S = RandomState> { /* private fields */ }

The ChainMap type. See the module level documentation for more.

Implementations

impl<K, V, S> ChainMap<K, V, S>

pub fn new() -> Self

Creates an empty ChainMap.

The chain is initially created with a capacity of 0, so it will not allocated until a HashMap is inserted into the chain.

Examples

use chain_map::ChainMap;
let mut chain: ChainMap<&str, i32> = ChainMap::new();

pub fn with_capacity(capacity: usize) -> Self

Creates a ChainMap with the specified capacity.

Will be able to hold at least capacity HashMaps without reallocating. If capacity is 0, the chain will not allocate.

Examples

use chain_map::ChainMap;
let mut chain: ChainMap<&str, i32> = ChainMap::with_capacity(10);

pub fn push_map(&mut self, map: HashMap<K, V, S>)

Appends a map to the lowest-precedence end of the chain

Panics

Panics if the number of maps in the chain overflows a usize.

Examples

use std::collections::HashMap;
use chain_map::ChainMap;

let mut hash = HashMap::new();
hash.insert("key", "value");

let mut chain = ChainMap::new();
chain.push_map(hash);

impl<K, V, S> ChainMap<K, V, S>

where K: Hash + Eq, S: BuildHasher,

pub fn contains_key<Q>(&self, k: &Q) -> bool

where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns true if the ChainMap contains a value for the given key.

As with HashMap::contains_key, the supplied key may be any borrowed form of the key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use std::collections::HashMap;
use chain_map::ChainMap;

let mut hash = HashMap::new();
hash.insert("key", "value");

let mut chain = ChainMap::new();
chain.push_map(hash);
assert!(chain.contains_key("key"));

pub fn get<Q>(&self, k: &Q) -> Option<&V>

where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns the highest-precedence value associated with the given key.

As with HashMap::get, the supplied key may be any borrowed form of the key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use std::collections::HashMap;
use chain_map::ChainMap;

let mut hash = HashMap::new();
hash.insert("key", "value");

let mut chain = ChainMap::new();
chain.push_map(hash);
assert_eq!(chain.get("key"), Some(&"value"));

Trait Implementations

impl<K: Clone, V: Clone, S: Clone> Clone for ChainMap<K, V, S>

fn clone(&self) -> ChainMap<K, V, S>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<K, V, S> Debug for ChainMap<K, V, S>

where K: Eq + Hash + Debug, V: Debug, S: BuildHasher,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<K, V, S> Default for ChainMap<K, V, S>

fn default() -> Self

Returns the “default value” for a type.

impl<K, V, S> Extend<HashMap<K, V, S>> for ChainMap<K, V, S>

fn extend<I>(&mut self, iter: I)

where I: IntoIterator<Item = HashMap<K, V, S>>,

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl<K, V, S> FromIterator<HashMap<K, V, S>> for ChainMap<K, V, S>

fn from_iter<I>(iter: I) -> Self

where I: IntoIterator<Item = HashMap<K, V, S>>,

Creates a value from an iterator.

impl<K, Q, V, S> Index<&Q> for ChainMap<K, V, S>

where K: Eq + Hash + Borrow<Q>, Q: Eq + Hash + ?Sized, S: BuildHasher,

type Output = V

The returned type after indexing.

fn index(&self, k: &Q) -> &V

Performs the indexing (container[index]) operation.

impl<K, V, S> PartialEq for ChainMap<K, V, S>

where K: Eq + Hash, V: PartialEq, S: BuildHasher,

fn eq(&self, other: &ChainMap<K, V, S>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<K, V, S> Eq for ChainMap<K, V, S>

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