b2pweb/bdf-collections

Collections implementations with java 8 stream like api.

v1.1.2 2020-09-18 08:04 UTC

This package is auto-updated.

Last update: 2021-11-30 11:04:14 UTC


README

Implementation of commons collections, with java-like stream to apply transformations.

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Installation with composer

composer require b2pweb/bdf-collections

Usage

Collections

All collections implements the Bdf\Collection\CollectionInterface interface.

A collection is a simple bag of elements, with a restricted set of methods :

  • add(mixed $element) Add the element to the collection. The implementation may reject the operation, and returns false.
  • addAll(iterator $elements) Equivalent to foreach ($elements as $element) { $collection->add($element); }.
  • clear() Remove all elements.
  • replace(iterable $elements) Clear and replace all elements.
  • empty() Check if the collection has no elements.
  • contains($element, bool $strict = false) Check if the collection contains the given element. If $strict is set to true, use strict comparison operator ===.
  • forEach(callable $callback) Iterates over all elements, using a callback.
  • toArray() Convert the collection to an array.
  • And inherited methods of IteratorAggregate, Countable and Streamable

The base behavior of collections is extended by other interfaces :

  • OrderedCollectionInterface : Ensure that all elements of the collection are ordered. Add (or modify) methods :
    • contains($element, bool $strict = false) Perform a binary search. The complexity of the call is O(log(n)) instead of O(n) on a simple collection.
    • search($element, bool $strict = false) Get the element position. Works like contains($element, bool $strict = false) but return the position instead of true. The expression $element == $collection->at($collection->search($element)) is always true when $element exists.
    • at(int $position) Get an element at the given position.
    • ArrayAccess methods, expects offsetSet(). Works with the position as offset.
  • SetInterface : Ensure that the collection no not contains any duplicated elements. Add (or modify) methods :
    • add($element) If the collection already contains the element, will return false, ignore the operation.
    • addAll(iterable $elements) Return false is at least on element is already added.
    • lookup($element) Find the corresponding elements stored into the Set.
  • TableInterface Add the key handling for modifying, or accessing elements :
    • set($key, $value) Set a value at the given key.
    • get($key) Get a value at the given key.
    • hasKey($key) Check if a key exists.
    • keys() Get all keys of the table.
    • values() Get all values as array. This is equivalent to iterator_to_array($collection)
    • forEach(callable $callback) Iterates over elements, but add the key as second argument of the callback.
    • ArrayAccess methods

ArrayCollection

The Bdf\Collection\ArrayCollection is the base implementation of TableInterface using an inner PHP array. It has great performances but do not handle complex key types, or optimised search.

Use as collection :

<?php
$collection = new ArrayCollection(['foo']);

$collection->contains('foo'); // true
$collection->contains('bar'); // false

$collection->add('bar');
$collection->contains('bar'); // true
$collection->remove('bar');
$collection->contains('bar'); // false

$collection->add(42);
$collection->contains('42', true); // false
$collection->contains(42, true); // true

// Print "foo 42"
$collection->forEach (function ($value) {
    echo $value, ' ';
});

// Same as above
foreach ($collection as $value) {
    echo $value, ' ';
}

Use as table :

<?php
$table = new ArrayCollection(['foo' => 'bar']);

// Using methods
$table->contains('bar'); // true
$table->hasKey('foo'); // true
$table->get('foo'); // "bar"

$table->set('value', 42);
$table->contains(42); // true

// Using array access
isset($table['value']); // true
$table['value']; // 42

$table->values(); // ['bar', 42]
$table->keys(); // ['foo', 'value]

// Print "foo=bar value=42"
$table->forEach (function ($value, $key) {
    echo $key, '=', $value, ' ';
});

// Same as above
foreach ($table as $key => $value) {
    echo $key, '=', $value, ' ';
}

OrderedCollection

Simple implementation of OrderedCollectionInterface. Do not sorts elements on modification, but only on access.

Usage :

<?php
$collection = new OrderedCollection();

$collection->addAll([4, 9, 2, 7]);

$collection->contains(9); // true
$collection->search(4); // 1
$collection->at(2); // 7
$collection->toArray(); // [2, 4, 7, 9]

$collection->remove(7);
$collection->toArray(); // [2, 4, 9]

// Array access
$collection[0]; // 2
isset($collection[9]); // false : check the existence of the offset
isset($collection[1]); // true
$collection[] = 5; // Add the element 5
unset($collection[2]); // Remove the 3rd element (5)

// Prints 0=2 4=1 9=2
$collection->forEach(function ($element, $position) {
    echo "$position=$element ";
});

// Same as above
foreach ($collection as $position => $element) {
    echo "$position=$element ";
}

// A custom comparator can also be used
$collection = new OrderedCollection(function ($a, $b) {
    return $a->compute() - $b->compute();
});

HashSet

A SetInterface implementation using an hash function for check the uniqueness of elements. Note: Unlike common HashSet implementations, like in java, only the hash code is used on comparison, and the equal operator is never used.

<?php

$set = new HashSet();

$set->add('foo'); // true
$set->add('foo'); // false : already added
$set->contains('foo'); // true
$set->contains('not found'); // false

// Works also with array or objects
$set->add(['foo' => 'bar']);

$obj = new stdClass();
$set->add($obj);

$set->lookup(new stdClass())->get() === $obj; // Get the stored element, which is equals with the parameter
$set->loopup('not found')->empty(); // true : An empty optional is returned if the element is not found

$objectSet = HashSet::spl(); // Use spl_object_hash() as hash function

$obj1 = new stdClass();
$obj2 = new stdClass();

$objectSet->add($obj1);
$objectSet->contains($obj1); // true
$objectSet->contains($obj2); // false : not the same reference, hash is different

HashTable

A more powerful and flexible implementation of TableInterface, using an hash function. This implementation is about 2 times slower than ArrayCollection. Unlike ArrayCollection, complex key types are supported (like objects).

Note: toArray() may failed if complex keys are used.

Usage :

<?php
// Use HashTable with multiple-keys indexing using array
$table = new HashTable();

$table[[123, 'aze']] = new Entity(1);
$table[[456, 'rty']] = new Entity(2);

$table[[123, 'aze']]; // Returns Entity(1)

// Use object as key
$table[new Key()] = 'value';

$table->toArray(false); // Associative array is not possible : return in form [ [key, value], ... ]

// Create a case insensitive table by registering a custom hash function
$ciTable = new HashTable('strtolower'); // Transform keys to lower case

$ciTable->set('Foo', 'bar');
$ciTable->get('FOO'); // 'bar'

Streams

Streams are used to transform collections elements. The streams implements Iterator, and can be used on a foreach. Each stream methods will return a new Stream instance :

  • map(callable $transformer) Apply $transformer to each values of the stream.
  • mapKey(callable $function) Apply $function to each values of the stream for generates keys.
  • filter(callable $predicate) Filter stream elements that are rejected by the predicate.
  • distinct(callable $hashFunction = null) Filter stream elements to get only distinct elements. A custom hash function can be used.
  • sort(callable $comparator = null, bool $preserveKeys = false) Order stream elements.
  • concat(StreamInterface $stream, bool $preserveKeys = true) Concatenate a new stream after the current stream.
  • flatMap(callable $transformer, bool $preserveKeys = false) Create a stream resulting of concatenation of each elements content extracted by $transformer.
  • skip(int $count) Skip the $count first elements of the stream.
  • limit(int $count, int $offset = 0) Limit the number of elements of the stream.
  • forEach(callable $consumer) Iterate over all stream elements.
  • toArray(bool $preserveKeys = true) Aggregate the stream to an array.
  • first() Get the first element of the stream.
  • reduce(callable $accumulator, $initial = null) Reduce all elements of the stream into a single value.
  • collect(CollectorInterface $collector) Collect all elements into a single value.
  • matchAll(callable $predicate) Check if all elements of the stream match with the predicate.
  • matchOne(callable $predicate) Check if at least one element of the stream match with the predicate.

Usage

$stream = Streams::wrap([7, 4, 9]);

// [ 10 => 8, 16 => 14, 20 => 18]
$stream
    ->sort()
    ->map(function ($element) { return $element * 2; })
    ->mapKey(function ($element) { return $element + 2; })
    ->toArray()
;

MutableArrayStream

The stream MutableArrayStream is an implementation of StreamInterface for simple PHP array. Unlike other streams, all transformations are applied on the method call, and $this is returned instead of a new stream instance. Reduce the overhead of the streams, for get better performances, but some methods has different behavior.

Usage :

$collection = new ArrayCollection([...]);

$stream = $collection->mutableStream(); // Get a mutable stream from an ArrayCollection
$stream = new MutableArrayStream([...]); // Or creates using constructor

// And use like other streams
$stream
    ->map(...)
    ->filter(...)
    ->collect(...)
;

Optional

The Bdf\Collection\Util\Optional is used to replace null value and null object. It permit to creates a simple null object. Methods :

  • filter(callable $predicate) Filter the optional value.
  • map(callable $transformer) Transform the element if it's present.
  • apply(callable $consumer) Apply the consumer on the element if it's present.
  • or($value) Get the current Optional value if it's present, or the parameter value if not present.
  • orThrows($exception = RuntimeException::class) Get the current value if present, or throws an exception.
  • orSupply(callable $supplier) Get the current value if present, or return the supplier result.
  • present() Check if the Optional value is present or not.
  • get() Get the current stored value.
  • Magic methods, which delegates to the inner object, and wrap the return value into an optional

Usage :

<?php

// Creates the optional
Optional::empty(); // "Null" optional
Optional::of($myValue); // Wrap $myValue into an Optional. The value must not be null
Optional::nullable($myValue); // Wrap $myValue into an Optional. The value may be null

Optional::empty()->present(); // false
Optional::of(42)->present(); // true

// Creates a simple null object
$myNullObject = Optional::nullable($person);

$myNullObject->firstName()->or('undefined'); // Call $person->firstName() if present, and get the return value, or return "undefined"
isset($myNullObject->myProp); // Check if property myProp exists into $person 

$myNullObject->stream(); // Creates a singleton or empty stream with the wrapped element.