CachingIterable<E> class

A lazy caching version of Iterable.

This iterable is efficient in the following ways:

  • It will not walk the given iterator more than you ask for.

  • If you use it twice (e.g. you check isNotEmpty, then use single), it will only walk the given iterator once. This caching will even work efficiently if you are running two side-by-side iterators on the same iterable.

  • toList uses its EfficientLength variant to create its list quickly.

It is inefficient in the following ways:

  • The first iteration through has caching overhead.

  • It requires more memory than a non-caching iterator.

  • the length and toList properties immediately precache the entire list. Using these fields therefore loses the laziness of the iterable. However, it still gets cached.

The caching behavior is propagated to the iterators that are created by map, where, expand, take, takeWhile, skip, and skipWhile, and is used by the built-in methods that use an iterator like isNotEmpty and single.

Because a CachingIterable only walks the underlying data once, it cannot be used multiple times with the underlying data changing between each use. You must create a new iterable each time. This also applies to any iterables derived from this one, e.g. as returned by where.

Inheritance

Constructors

CachingIterable(Iterator<E> _prefillIterator)
Creates a CachingIterable using the given Iterator as the source of data. The iterator must be non-null and must not throw exceptions. [...]

Properties

iterator Iterator<E>
Returns a new Iterator that allows iterating the elements of this Iterable. [...]
read-only
length int
Returns the number of elements in this. [...]
read-only
first → E
Returns the first element. [...]
read-only, inherited
hashCode int
The hash code for this object. [...]
read-only, inherited
isEmpty bool
Returns true if there are no elements in this collection. [...]
read-only, inherited
isNotEmpty bool
Returns true if there is at least one element in this collection. [...]
read-only, inherited
last → E
Returns the last element. [...]
read-only, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
single → E
Checks that this iterable has only one element, and returns that element. [...]
read-only, inherited

Methods

expand<T>(Iterable<T> f(E element)) Iterable<T>
Expands each element of this Iterable into zero or more elements. [...]
map<T>(T f(E e)) Iterable<T>
Returns a new lazy Iterable with elements that are created by calling f on each element of this Iterable in iteration order. [...]
skip(int count) Iterable<E>
Returns an Iterable that provides all but the first count elements. [...]
skipWhile(bool test(E value)) Iterable<E>
Returns an Iterable that skips leading elements while test is satisfied. [...]
take(int count) Iterable<E>
Returns a lazy iterable of the count first elements of this iterable. [...]
takeWhile(bool test(E value)) Iterable<E>
Returns a lazy iterable of the leading elements satisfying test. [...]
toList({bool growable: true }) List<E>
Creates a List containing the elements of this Iterable. [...]
where(bool test(E element)) Iterable<E>
Returns a new lazy Iterable with all elements that satisfy the predicate test. [...]
any(bool test(E element)) bool
Checks whether any element of this iterable satisfies test. [...]
inherited
cast<R>() Iterable<R>
Provides a view of this iterable as an iterable of R instances. [...]
inherited
contains(Object element) bool
Returns true if the collection contains an element equal to element. [...]
inherited
elementAt(int index) → E
Returns the indexth element. [...]
inherited
every(bool test(E element)) bool
Checks whether every element of this iterable satisfies test. [...]
inherited
firstWhere(bool test(E element), { E orElse() }) → E
Returns the first element that satisfies the given predicate test. [...]
inherited
fold<T>(T initialValue, T combine(T previousValue, E element)) → T
Reduces a collection to a single value by iteratively combining each element of the collection with an existing value [...]
inherited
followedBy(Iterable<E> other) Iterable<E>
Returns the lazy concatentation of this iterable and other. [...]
inherited
forEach(void f(E element)) → void
Applies the function f to each element of this collection in iteration order.
inherited
join([String separator = "" ]) String
Converts each element to a String and concatenates the strings. [...]
inherited
lastWhere(bool test(E element), { E orElse() }) → E
Returns the last element that satisfies the given predicate test. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
@pragma('vm:entry-point'), inherited
reduce(E combine(E value, E element)) → E
Reduces a collection to a single value by iteratively combining elements of the collection using the provided function. [...]
inherited
singleWhere(bool test(E element), { E orElse() }) → E
Returns the single element that satisfies test. [...]
inherited
toSet() Set<E>
Creates a Set containing the same elements as this iterable. [...]
inherited
toString() String
Returns a string representation of (some of) the elements of this. [...]
inherited
whereType<T>() Iterable<T>
Returns a new lazy Iterable with all elements that have type T. [...]
inherited

Operators

operator ==(dynamic other) bool
The equality operator. [...]
inherited