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A set of utility libraries for Dart that makes using many Dart libraries easier and more convenient, or adds additional functionality.

Build Status Coverage Status Pub


API Docs are available.

Main Libraries


Utilities for working with Futures, Streams and async computations.

collect collects the completion events of an Iterable of Futures into a Stream.

enumerate and concat represent Stream versions of the same-named quiver.iterables methods.

StreamBuffer allows for the orderly reading of elements from a stream, such as a socket.

FutureStream turns a Future<Stream> into a Stream which emits the same events as the stream returned from the future.

StreamRouter splits a Stream into multiple streams based on a set of predicates.

CountdownTimer is a simple countdown timer that fires events in regular increments.

Metronome is a self-correcting alternative to Timer.periodic. It provides a simple, tracking periodic stream of DateTime events with optional anchor time.

stringFromByteStream constructs a string from a stream of byte lists.


Cache is a semi-persistent, asynchronously accessed, mapping of keys to values. Caches are similar to Maps, except that the cache implementation might store values in a remote system, so all operations are asynchronous, and caches might have eviction policies.

MapCache is a Cache implementation backed by a Map.


checkArgument throws ArgumentError if the specified argument check expression is false.

checkListIndex throws RangeError if the specified index is out of bounds.

checkState throws StateError if the specified state check expression is false.


listsEqual, mapsEqual and setsEqual check collections for equality.

indexOf finds the first index of an item satisfying a predicate.

LruMap is a map that removes the least recently used item when a threshold length is exceeded.

Multimap is an associative collection that maps keys to collections of values.

BiMap is a bidirectional map and provides an inverse view, allowing lookup of key by value.

TreeSet is a balanced binary tree that offers a bidirectional iterator, the ability to iterate from an arbitrary anchor, and ‘nearest’ search.


Optional is a way to represent optional values without allowing null.

hashObjects, hash2, hash3, and hash4 generate high-quality hashCodes for a list of objects, or 2, 3, or 4 arguments respectively.


concat, count, cycle, enumerate, merge, partition, range, and zip create, transform, or combine Iterables in different ways, similar to Python's itertools.

min, max, and extent retrieve the minimum and maximum elements from an iterable.

GeneratingIterable is an easy way to create lazy iterables that produce elements by calling a function. A common use-case is to traverse properties in an object graph, like the parent relationship in a tree.

InfiniteIterable is a base class for Iterables that throws on operations that require a finite length.


pattern.dart container utilities for work with Patterns and RegExps.

Glob implements glob patterns that are commonly used with filesystem paths.

matchesAny combines multiple Patterns into one, and allows for exclusions.

matchesFull returns true if a Pattern matches an entire String.

escapeRegex escapes special regex characters in a String so that it can be used as a literal match inside of a RegExp.


isBlank checks if a string is null, empty or made of whitespace characters.

isNotBlank checks if a string is not null, and not blank.

isEmpty checks if a string is null or empty.

isNotEmpty checks if a string is not null and not empty.

equalsIgnoreCase checks if two strings are equal, ignoring case.

compareIgnoreCase compares two strings, ignoring case.

loop allows you to loop through characters in a string starting and ending at arbitrary indices. Out of bounds indices allow you to wrap around the string, supporting a number of use-cases, including:

  • Rotating: loop('lohel', -3, 2) => 'hello'
  • Repeating, like String's operator*, but with better character-level control, e.g.: loop('la ', 0, 8) => 'la la la' // no trailing space
  • Tailing: loop('/path/to/some/file.txt', -3) => 'txt'
  • Reversing: loop('top', 3, 0) => 'pot'


Clock provides points in time relative to the current point in time, for example: now, 2 days ago, 4 weeks from now, etc. For testability, use Clock rather than other ways of accessing time, like new DateTime(), so that you can use a fake time function in your tests to control time.

Now is a typedef for functions that return the current time in microseconds, since Clock deals in DateTime which only have millisecond accuracy.

aMicrosecond, aMillisecond, aSecond, aMinute, anHour, aDay, and aWeek are unit duration constants to allow writing for example:

  • aDay vs. const Duration(days: 1)
  • aSecond * 30 vs. const Duration(seconds: 30)

Testing Libraries

The Quiver testing libraries are intended to be used in testing code, not production code. It currently consists of fake implementations of some Quiver interfaces.


FakeAsync enables testing of units which depend upon timers and microtasks. It supports fake advancements of time and the microtask queue, which cause fake timers and microtasks to be processed. A Clock is provided from which to read the current fake time. Faking synchronous or blocking time advancement is also supported.


areEqualityGroups is a matcher that supports testing operator== and hashCode implementations.


FakeStopwatch is a Stopwatch that uses a provided now() function to get the current time.