├── LICENSE ├── README.md ├── composer.json └── src ├── Deferred.php ├── Immediate.php ├── Interfaces └── Deferred.php └── functions.php /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. Definitions. 8 | 9 | "License" shall mean the terms and conditions for use, reproduction, 10 | and distribution as defined by Sections 1 through 9 of this document. 11 | 12 | "Licensor" shall mean the copyright owner or entity authorized by 13 | the copyright owner that is granting the License. 14 | 15 | "Legal Entity" shall mean the union of the acting entity and all 16 | other entities that control, are controlled by, or are under common 17 | control with that entity. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright {yyyy} {name of copyright owner} 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | [![Latest Stable Version](https://poser.pugx.org/sanmai/later/v/stable)](https://packagist.org/packages/sanmai/later) 2 | ![CI](https://github.com/sanmai/later/workflows/CI/badge.svg) 3 | [![Coverage Status](https://coveralls.io/repos/github/sanmai/later/badge.svg?branch=main)](https://coveralls.io/github/sanmai/later?branch=main) 4 | [![Type Coverage](https://shepherd.dev/github/sanmai/later/coverage.svg)](https://shepherd.dev/github/sanmai/later) 5 | 6 | This rigorously tested fully-typed library just works. It neither defines nor throws any exceptions. 7 | 8 | # Install 9 | 10 | ``` 11 | composer require sanmai/later 12 | ``` 13 | 14 | The latest version requires PHP 7.4 or greater. 15 | 16 | # Use 17 | 18 | To use this pattern you need a generator function, yielding a single item of type you want to produce lazily. Pass it to `later()`, a static wrapper returning a `Deferred` object: 19 | 20 | For example: 21 | 22 | ```php 23 | use function Later\later; 24 | 25 | $deferred = later(function () { 26 | $deepThought = new DeepThought(); 27 | $deepThought->solveTheQuestion(); 28 | 29 | yield $deepThought; 30 | }); 31 | ``` 32 | 33 | And then call `get()` when needed, as many times as needed: 34 | 35 | ```php 36 | $deferred->get()->getAnswer(); // 42 37 | $deferred->get()->getAnswer(); // same 42 38 | ``` 39 | 40 | Using a generator instead of a traditional callback comes with a major benefit: any generator is guaranteed by the language to be used exactly once. You can be sure that it won't be called twice. 41 | 42 | But that's not all: read on. 43 | 44 | ## No Callbacks Required 45 | 46 | Making a closure generator on the spot isn't always convenient. And not to say these closures are much different from all-too-familiar callbacks. Not at all different from the looks of them. 47 | 48 | The power of this pattern is in its ability to make use of any function, previously returning a single value, without any need for any additional callbacks or closures. 49 | 50 | Consider this diff: 51 | 52 | ```diff 53 | private function makeFooBar() 54 | { 55 | //... 56 | 57 | - return $foo; 58 | + yield $foo; 59 | } 60 | ``` 61 | 62 | After adding `Later\lazy` to the mix: 63 | 64 | ```diff 65 | use function Later\lazy; 66 | 67 | public function __construct() 68 | { 69 | - $this->fooBar = $this->makeFooBar(); 70 | + $this->lazyFooBar = lazy($this->makeFooBar()); 71 | } 72 | 73 | public function usesFooBar() 74 | { 75 | if ($fooBarReallyRequired) { 76 | - $this->fooBar->getResult(); 77 | + $this->lazyFooBar->get()->getResult(); 78 | } 79 | } 80 | ``` 81 | 82 | We can see, this simple, single-line, change in the original method freed our program from creating things it may not need, postponing this process until the last moment, while also avoiding any use of callbacks. 83 | 84 | ## Type Transparency 85 | 86 | The library is completely typed. [PHPStan](https://github.com/phpstan/phpstan), [Psalm](https://github.com/vimeo/psalm), and [Phan](https://github.com/phan/phan) are all routinely supported. 87 | 88 | To use this capability it is recommended to declare a variable holding this object as `\Later\Interfaces\Deferred`. 89 | 90 | In this example it will be `Deferred`: 91 | 92 | ```php 93 | use Later\Interfaces\Deferred; 94 | use function Later\lazy; 95 | 96 | final class HyperIntelligentMice 97 | { 98 | /** @var Deferred */ 99 | private $supercomputer; 100 | 101 | public function __construct(DeepThought $deepThought) 102 | { 103 | $this->supercomputer = lazy(self::updateDeepThought($deepThought)); 104 | } 105 | 106 | /** @return iterable */ 107 | private static function updateDeepThought(DeepThought $deepThought): iterable 108 | { 109 | $deepThought->solveTheQuestion(); 110 | 111 | yield $deepThought; 112 | } 113 | 114 | public function getAnswer(): int 115 | { 116 | return $this->supercomputer->get()->getAnswer(); 117 | } 118 | } 119 | ``` 120 | 121 | Following this approach, a static analyzer or IDE will be able to understand what is called, and what is returned. 122 | 123 | ### Proxy Syntax 124 | 125 | The library supports convenient proxy syntax for accessing methods and properties directly from the deferred object: 126 | 127 | ```php 128 | /** @var \Later\Interfaces\Deferred $deferred */ 129 | $deferred->getAnswer(); // 42 130 | $deferred->answer; // 42 131 | ``` 132 | 133 | With the explicit type IDEs such as PhpStorm can autocomplete proxied members. 134 | 135 | ## Eager Execution 136 | 137 | What if a program calls for `Deferred` object, but lazy evaluation is not required? For example, because a result is already available being loaded from a cache. 138 | 139 | No problem, there's a function for this: 140 | 141 | ```php 142 | use function Later\now; 143 | 144 | $deferred = now($result); 145 | $deferred->get(); // returns $result 146 | ``` 147 | 148 | This deferred-but-not-deferred object implements the same interface, and can be used anywhere where a normal `Deferred` object would go. 149 | 150 | # Writing Tests 151 | 152 | The underlying `Deferred` object is fairly lax about input types. It will be happy to accept any `iterable`, not just generators. 153 | 154 | This makes it super easy to use in mocks: 155 | 156 | ```php 157 | use function Later\lazy; 158 | 159 | $this->lazyDependency = lazy([ 160 | $myDependency, 161 | ]); 162 | ``` 163 | 164 | Yet for constant and already-known answers best to use a non-deferred variant: 165 | 166 | ```php 167 | use function Later\now; 168 | 169 | $this->lazyDependency = now($myDependency); 170 | ``` 171 | 172 | And that's it. No need to go through loops assembling closures and whatnot. 173 | 174 | If nothing else, one can make a common mock for it: 175 | 176 | ```php 177 | $deferredMock = $this->createMock(\Later\Interfaces\Deferred::class); 178 | $deferredMock 179 | ->expects($this->once()) 180 | ->method('get') 181 | ->willReturn($myDependency) 182 | ; 183 | ``` 184 | 185 | # API Overview 186 | 187 | | Method | Takes | Returns | 188 | | --------------- | ---------------------------- | ------------------------------- | 189 | | `Later\lazy()` | `iterable` | `\Later\Interfaces\Deferred` | 190 | | `Later\later()` | A generator callback for `T` | `\Later\Interfaces\Deferred` | 191 | | `Later\now()` | `T` | `\Later\Interfaces\Deferred` | 192 | -------------------------------------------------------------------------------- /composer.json: -------------------------------------------------------------------------------- 1 | { 2 | "name": "sanmai/later", 3 | "description": "Later: deferred wrapper object", 4 | "license": "Apache-2.0", 5 | "type": "library", 6 | "authors": [ 7 | { 8 | "name": "Alexey Kopytko", 9 | "email": "alexey@kopytko.com" 10 | } 11 | ], 12 | "require": { 13 | "php": ">=8.2" 14 | }, 15 | "require-dev": { 16 | "ergebnis/composer-normalize": "^2.8", 17 | "friendsofphp/php-cs-fixer": "^3.35.1", 18 | "infection/infection": ">=0.27.6", 19 | "phan/phan": ">=2", 20 | "php-coveralls/php-coveralls": "^2.0", 21 | "phpstan/phpstan": ">=1.4.5", 22 | "phpunit/phpunit": ">=9.5 <10", 23 | "vimeo/psalm": ">=2" 24 | }, 25 | "autoload": { 26 | "psr-4": { 27 | "Later\\": "src/" 28 | }, 29 | "files": [ 30 | "src/functions.php" 31 | ] 32 | }, 33 | "autoload-dev": { 34 | "psr-4": { 35 | "Tests\\Later\\": "tests/" 36 | } 37 | }, 38 | "config": { 39 | "sort-packages": true, 40 | "allow-plugins": true 41 | }, 42 | "extra": { 43 | "branch-alias": { 44 | "dev-main": "0.1.x-dev" 45 | } 46 | } 47 | } 48 | -------------------------------------------------------------------------------- /src/Deferred.php: -------------------------------------------------------------------------------- 1 | 5 | * 6 | * Licensed under the Apache License, Version 2.0 (the "License"); 7 | * you may not use this file except in compliance with the License. 8 | * You may obtain a copy of the License at 9 | * 10 | * http://www.apache.org/licenses/LICENSE-2.0 11 | * 12 | * Unless required by applicable law or agreed to in writing, software 13 | * distributed under the License is distributed on an "AS IS" BASIS, 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 | * See the License for the specific language governing permissions and 16 | * limitations under the License. 17 | */ 18 | 19 | declare(strict_types=1); 20 | 21 | namespace Later; 22 | 23 | use Throwable; 24 | use Override; 25 | 26 | /** 27 | * Deferred: a wrapper object. 28 | * 29 | * @template T 30 | * @mixin T 31 | * 32 | * @template-implements Interfaces\Deferred 33 | * 34 | * @internal 35 | * @final 36 | */ 37 | class Deferred implements Interfaces\Deferred 38 | { 39 | /** 40 | * @var ?iterable 41 | */ 42 | private ?iterable $input; 43 | 44 | /** 45 | * @var T 46 | */ 47 | private $output; 48 | 49 | private ?Throwable $error; 50 | 51 | /** 52 | * @param iterable $input 53 | */ 54 | public function __construct(iterable $input) 55 | { 56 | $this->input = $input; 57 | $this->error = null; 58 | } 59 | 60 | /** 61 | * @return T 62 | */ 63 | #[Override] 64 | public function get() 65 | { 66 | if (null !== $this->error) { 67 | throw $this->error; 68 | } 69 | 70 | if (null === $this->input) { 71 | return $this->output; 72 | } 73 | 74 | try { 75 | foreach ($this->input as $output) { 76 | $this->output = $output; 77 | 78 | break; 79 | } 80 | } catch (Throwable $e) { 81 | $this->error = $e; 82 | 83 | throw $e; 84 | } finally { 85 | $this->input = null; 86 | } 87 | 88 | return $this->output; 89 | } 90 | 91 | /** 92 | * Forwards the call to the resolved object; PHP throws \Error if the method is missing. 93 | * MixedMethodCall is suppressed because Psalm cannot infer methods on the generic type. 94 | * 95 | * @param array $args Forwarded variadic arguments. 96 | * @psalm-suppress MixedMethodCall 97 | */ 98 | public function __call(string $name, array $args): mixed 99 | { 100 | return $this->get()->{$name}(...$args); 101 | } 102 | 103 | public function __get(string $name): mixed 104 | { 105 | return $this->get()->$name; 106 | } 107 | } 108 | -------------------------------------------------------------------------------- /src/Immediate.php: -------------------------------------------------------------------------------- 1 | 5 | * 6 | * Licensed under the Apache License, Version 2.0 (the "License"); 7 | * you may not use this file except in compliance with the License. 8 | * You may obtain a copy of the License at 9 | * 10 | * http://www.apache.org/licenses/LICENSE-2.0 11 | * 12 | * Unless required by applicable law or agreed to in writing, software 13 | * distributed under the License is distributed on an "AS IS" BASIS, 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 | * See the License for the specific language governing permissions and 16 | * limitations under the License. 17 | */ 18 | 19 | declare(strict_types=1); 20 | 21 | namespace Later; 22 | 23 | use Override; 24 | 25 | /** 26 | * Immediate: a wrapper object. 27 | * 28 | * @template T 29 | * 30 | * @template-implements Interfaces\Deferred 31 | * 32 | * @internal 33 | * @final 34 | */ 35 | class Immediate implements Interfaces\Deferred 36 | { 37 | /** 38 | * @var T 39 | */ 40 | private $output; 41 | 42 | /** 43 | * @param T $input 44 | */ 45 | public function __construct($input) 46 | { 47 | $this->output = $input; 48 | } 49 | 50 | /** 51 | * @return T 52 | */ 53 | #[Override] 54 | public function get() 55 | { 56 | return $this->output; 57 | } 58 | } 59 | -------------------------------------------------------------------------------- /src/Interfaces/Deferred.php: -------------------------------------------------------------------------------- 1 | 5 | * 6 | * Licensed under the Apache License, Version 2.0 (the "License"); 7 | * you may not use this file except in compliance with the License. 8 | * You may obtain a copy of the License at 9 | * 10 | * http://www.apache.org/licenses/LICENSE-2.0 11 | * 12 | * Unless required by applicable law or agreed to in writing, software 13 | * distributed under the License is distributed on an "AS IS" BASIS, 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 | * See the License for the specific language governing permissions and 16 | * limitations under the License. 17 | */ 18 | 19 | declare(strict_types=1); 20 | 21 | namespace Later\Interfaces; 22 | 23 | /** 24 | * @template T 25 | * @mixin T 26 | */ 27 | interface Deferred 28 | { 29 | /** 30 | * @return T 31 | */ 32 | public function get(); 33 | } 34 | -------------------------------------------------------------------------------- /src/functions.php: -------------------------------------------------------------------------------- 1 | 5 | * 6 | * Licensed under the Apache License, Version 2.0 (the "License"); 7 | * you may not use this file except in compliance with the License. 8 | * You may obtain a copy of the License at 9 | * 10 | * http://www.apache.org/licenses/LICENSE-2.0 11 | * 12 | * Unless required by applicable law or agreed to in writing, software 13 | * distributed under the License is distributed on an "AS IS" BASIS, 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 | * See the License for the specific language governing permissions and 16 | * limitations under the License. 17 | */ 18 | 19 | declare(strict_types=1); 20 | 21 | namespace Later; 22 | 23 | /** 24 | * @template T 25 | * 26 | * @param callable():(iterable) $generator 27 | * 28 | * @return Interfaces\Deferred 29 | */ 30 | function later(callable $generator): Interfaces\Deferred 31 | { 32 | return new Deferred($generator()); 33 | } 34 | 35 | /** 36 | * @template T 37 | * 38 | * @param iterable $iterableOrGenerator 39 | * 40 | * @return Interfaces\Deferred 41 | */ 42 | function lazy(iterable $iterableOrGenerator): Interfaces\Deferred 43 | { 44 | return new Deferred($iterableOrGenerator); 45 | } 46 | 47 | /** 48 | * @template T 49 | * 50 | * @param T $input 51 | * 52 | * @return Interfaces\Deferred 53 | */ 54 | function now($input): Interfaces\Deferred 55 | { 56 | return new Immediate($input); 57 | } 58 | --------------------------------------------------------------------------------