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

Build Status


API Docs can be found here: http://google.github.io/quiver-dart/docs/


Add Quiver to your project's pubspec.yaml file and run pub get. We reccomend the following version constraint:

  quiver: '>=0.13.0<0.14.0'

Main Libraries


Utilities for working with Futures, Streams and async computations.

FutureGroup is collection of Futures that signals when all its child futures have completed. Allows adding new Futures as long as it hasn't completed yet. Useful when async tasks can spwn new async tasks and you need to wait for all of them to complete.

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

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

doWhileAsync, reduceAsync and forEachAsync perform async computations on the elements of on Iterables, waiting for the computation to complete before processing the next element.

CreateTimer and CreateTimerPeriodic are typedefs that are useful for passing Timer factories to classes and functions, increasing the testability of code that depends on Timer.


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.


listsEqual and mapsEqual check collections for equality.

Multimap is an associative collection that maps keys to collections of values. BiMap is a bi-directional map and provides an inverse view, allowing lookup of key by value.


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

firstNonNull returns its first non-null argument.

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


visitDirectory is a recursive directory lister that conditionally recurses into sub-directories based on the result of a handler function.


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

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


getTypeName returns the name of a Type instance.

implements and classImplements determine if an instance or ClassMirror, respectively, implement the interface represented by a Type instance. They implement the behavior of is for mirrors, except for generics.

getMemberMirror searches though a ClassMirror and its class hierarchy for a member. This makes up for the fact that ClassMirror.members doesn't contain members from interfaces or superclasses.

Method wraps an InstanceMirror and Symbol to create a callable that invokes a method on the instance. It in effect closurizes a method reflectively.


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.

equalsIgnoreCase checks if two strings are equal, ignoring case.

compareIgnoreCase compares two strings, ignoring case.

flip flips the order of characters in a string.

nullToEmpty turns null to empty string, and returns non-empty strings unchanged.

emptyToNull turns empty string to null, and returns non-empty strings unchanged.

repeat concatenates a string to itself a given number of times, for example:

repeat('la ', 3) => 'la la la '

It can also repeat in reverse, for example:

repeat(' og', -3) => 'go go go '

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 repeat, but with better character-level control, e.g.: loop('la ', 0, 8) => 'la la la' // no tailing space

  • Tailing: loop('/path/to/some/file.txt', -3) => 'txt'
  • Reversing: loop('top', 3, 0) => 'pot'

padLeft and padRight pad strings to a given width.


Clock provides points in time relative to the current point in time, for example: now, 2 days ago, 4 weeks from now, etc. For tesability, 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.

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.


FakeTimer is a Timer that captures its duration and callback for use in tests.


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



Collection classes and related utilities.


Simple code with broad use cases.


This library contains utilities for working with RegExps and other Patterns.


Testing support for dart:async.


Testing support related to the Dart runtime.


Testing support for dart:core time functionality.