README

A functional programming library for PHP. Inspired by Underscore, Lodash, and Ramda.

$avgMaleAge = Dash\chain([
	['name' => 'John', 'age' => 12, 'gender' => 'male'],
	['name' => 'Jane', 'age' => 34, 'gender' => 'female'],
	['name' => 'Pete', 'age' => 23, 'gender' => 'male'],
	['name' => 'Mark', 'age' => 11, 'gender' => 'male'],
	['name' => 'Mary', 'age' => 42, 'gender' => 'female'],
])
->filter(['gender', 'male'])
->map('age')
->average()
->value();

echo "Average male age is $avgMaleAge.";

Operations

View full list of operations here

Highlights

Many data types supported: arrays, objects, generators (coming soon), Traversable, DirectoryIterator, and more
Chaining
Currying
Lazy evaluation
Custom operations
Well-tested: Comprehensive tests with nearly 3,000 test cases and 100% code coverage

Why use Dash?

PHP's built-in array_* functions are limited, difficult to compose, inconsistent, and don't work across many data types.

For instance, let's say we want to find the average age of males in this list:

$people = [
	['name' => 'John', 'age' => 12, 'gender' => 'male'],
	['name' => 'Jane', 'age' => 34, 'gender' => 'female'],
	['name' => 'Pete', 'age' => 23, 'gender' => 'male'],
	['name' => 'Mark', 'age' => 11, 'gender' => 'male'],
	['name' => 'Mary', 'age' => 42, 'gender' => 'female'],
];

Using PHP's built-in in functions, we might write something like this:

$males = array_filter($people, function ($person) {
	return $person['gender'] === 'male';
});
$avgMaleAge = array_sum(array_column($males, 'age')) / count($males);

Dash makes common data transformation operations simpler:

$avgMaleAge = Dash\chain($people)
	->filter(['gender', 'male'])
	->map('age')
	->average()
	->value();

This is just a tiny subset of what Dash can do. See the full list of operations here.

Installation

Requires PHP 7.4+

composer require mpetrovich/dash

Usage

Dash operations are pure functions that can be used alone or chained together.

Standalone

Operations can be called as namespaced functions:

Dash\map([1, 2, 3], function ($n) { return $n * 2; });  // === [2, 4, 6]

or as static methods:

use Dash\Dash;

Dash::map([1, 2, 3], function ($n) { return $n * 2; });  // === [2, 4, 6]

Dash\_ can also be used as an alias for Dash\Dash:

use Dash\_;

_::map([1, 2, 3], function ($n) { return $n * 2; });  // === [2, 4, 6]

Chaining

Multiple operations can be chained in sequence using chain(). Call value() to return the final value.

$result = Dash\chain([1, 2, 3, 4, 5])
	->filter('Dash\isOdd')
	->map(function ($n) { return $n * 2; })
	->value();

// $result === [2, 6, 10]

To explicitly convert the value to an array or stdClass, use arrayValue() or objectValue() respectively:

$result = Dash\chain(['a' => 1, 'b' => 2, 'c' => 3])
	->filter('Dash\isOdd')
	->mapValues(function ($n) { return $n * 2; })
	->objectValue();

// $result === (object) ['a' => 2, 'c' => 6]

For convenience, Dash\chain() can be aliased to a global function using addGlobalAlias(). It only needs to be called once during your application bootstrap:

// In your application bootstrap:
Dash::addGlobalAlias('__');

// Elsewhere:
$result = __([1, 2, 3, 4, 5])
	->filter('Dash\isOdd')
	->map(function ($n) { return $n * 2; })
	->value();

Sometimes you don't need the return value of the chain. However, the chain isn't processed until value() is called. For semantic convenience, run() is also an alias for value():

$chain = Dash\chain(range(1, 5))
	->reverse()
	->each(function ($n) {
		echo "T-minus $n...\n";
		sleep(1);
	});

// Nothing echoed yet

$chain->value();
// or
$chain->run();

// Echoes each of the following lines 1 second apart:
// T-minus 5...
// T-minus 4...
// T-minus 3...
// T-minus 2...
// T-minus 1...

Supported data types

Dash can work with a wide variety of data types, including:

arrays
objects (eg. stdClass)
generators (still in development)
anything that implements the Traversable interface
DirectoryIterator, which is also a Traversable but cannot normally be used with iterator_to_array() due to a PHP bug. Dash works around this transparently.

Examples

With an array:

Dash\chain([1, 2, 3, 4])
	->filter('Dash\isEven')
	->map(function ($value) {
		return $value * 2;
	})
	->value();
// === [4, 8]

With an object:

Dash\chain((object) ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4])
	->filter('Dash\isOdd')
	->keys()
	->join(', ')
	->value();
// === 'a, c'

With a Traversable:

Dash\chain(new ArrayObject(['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4]))
	->pick(['b', 'c'])
	->values()
	->sum()
	->value();
// === 5

With a DirectoryIterator:

$iterator = new FilesystemIterator(__DIR__, FilesystemIterator::SKIP_DOTS);

$filenames = Dash\chain($iterator)
	->reject(function ($fileinfo) {
		return $fileinfo->isDir();
	})
	->map(function ($fileinfo) {
		return pathinfo($fileinfo)['filename'];
	})
	->value();

Currying

curry() and related operations can be used to create curried functions from any callable:

function listThree($a, $b, $c) {
	return "$a, $b, and $c";
}

$listThree = Dash\curry('listThree');
$listTwo = $listThree('first');
$listTwo('second', 'third');  // === 'first, second, and third'

Most Dash functions have a curried version that accepts input data as the last parameter instead of as the first. Curried versions are located in the Dash\Curry namespace:

Dash\chain([
	'a' => 3,
	'b' => '3',
	'c' => 3,
	'd' => 3.0
])
->filter(Dash\Curry\identical(3))
->value();
// === ['a' => 3, 'c' => 3]

Similarly, partial() and related operations can be used to create partially-applied functions:

$greet = function ($greeting, $name) {
	return "$greeting, $name!";
};

$sayHello = Dash\partial($greet, 'Hello');
$sayHowdy = Dash\partial($greet, 'Howdy');

$sayHello('Mark');  // === 'Hello, Mark!'
$sayHowdy('Jane');  // === 'Howdy, Jane!'

Lazy evaluation

Chained operations are not evaluated until value() or run() is called. Furthermore, the input data can be changed and evaluated multiple times using with(). This makes it simple to create reusable chains:

$chain = Dash\chain()
	->filter('Dash\isOdd')
	->map(function ($n) { return $n * 2; });

$chain->with([1, 2, 3])->value();  // === [2, 6]
$chain->with([4, 5, 6, 7])->value();  // === [10, 14]

Chains can also be cloned and extended:

// …continued from above
$clone = clone $chain;
$clone->map(function ($n) { $n + 1; })
$clone->value();  // === [11, 15]

// The original chain is untouched
$chain->value();  // === [10, 14]

When value() is called, the result is cached until the chain is modified or the input is changed using with().

Custom operations

Custom operations can be added, retrieved, and removed using setCustom(), getCustom(), and unsetCustom(), respectively. Dash\custom() is also an alias for Dash::getCustom():

Dash::setCustom('triple', function ($n) { return $n * 3; });

// Standalone
Dash::triple(4);  // === 12

// Chained
Dash\chain([1, 2, 3])
	->sum()
	->triple()
	->value();  // === 18

// As an argument
Dash\chain([1, 2, 3])
	->map('Dash\Dash::triple')
	->value();  // === [3, 6, 9]

// As an argument using the Dash::getCustom() method
Dash\chain([1, 2, 3])
	->map(Dash::getCustom('triple'))
	->value();  // === [3, 6, 9]

// Using the Dash\custom() operation
Dash\chain([1, 2, 3])
	->map(Dash\custom('triple'))
	->value();  // === [3, 6, 9]

Dash::unsetCustom('triple');

When chained, the current input is passed as the first parameter to the custom operation:

Dash::setCustom('divide', function($numerator, $denominator) { return $numerator / $denominator; });

Dash\chain(6)->divide(2)->value();  // === 2

Tips

If you find that Dash doesn't have an operation that you need, fear not. Custom logic can be added without giving up Dash chaining or other features. The simplest way to integrate missing operations is via the Dash\thru() operation, which allows custom logic to modify and seamlessly pass through its results to the next step in the chain.

For example, suppose we want to use array_change_key_case() and keep the usual Dash chaining semantics. With thru(), it's simple:

$result = Dash\chain(['one' => 1, 'two' => 2, 'three' => 3])
	->filter('Dash\isOdd')
	->thru(function($input) {
		return array_change_key_case($input, CASE_UPPER);
	})
	->keys()
	->value();

// $result === ['ONE', 'THREE']

Alternatively, if you find yourself needing to use array_change_key_case() often, it may be better to add a new custom operation:

Dash::setCustom('keyCase', function ($input, $case) {
	return array_change_key_case($input, $case);
});

which you can then use like any other chainable Dash method:

$result = Dash\chain(['one' => 1, 'two' => 2, 'three' => 3])
	->filter('Dash\isOdd')
	->keyCase(CASE_UPPER)
	->keys()
	->value();

// $result === ['ONE', 'THREE']

Feedback

Found a bug or have a suggestion? Please create a new GitHub issue. We want your feedback!

mpetrovich / dash

Maintainers

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