functional approach in software design Tomasz Kowalczyk @tmmx 

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introduction 

purpose 

levels 

level 0: approach 

paradigm shift 

SOLID 

immutability 

higher order functions 

composition 

level 1: operations 

casual conditionals 

$result = []; foreach($this->users as $user) { if($user->isDisabled()) { continue; } if($user->isHidden()) { continue; } $result[] = $user; } return $result; 

$result = []; foreach($this->users as $user) { if($user->isDisabled()) { continue; } if($user->isHidden()) { continue; } $result[] = $user; } return $result; 

$isEnabled = function(User $u): bool { return false === $u->isDisabled(); }; $isVisible = function(User $u): bool { return false === $u->isHidden(); }; return array_filter( array_filter($this->users, $isVisible), $isEnabled); 

$isEnabled = function(User $u): bool { return false === $u->isDisabled(); }; $isVisible = function(User $u): bool { return false === $u->isHidden(); }; return $this->users ->filter($isVisible) ->filter($isEnabled); 

endless loops 

$ids = []; foreach($this->users as $user) { foreach($user->getTags() as $tag) { $tagId = $tag->getId(); if(false === in_array($tagId, $ids, true)) { $ids[] = $tagId; } } } return $ids; 

$ids = []; foreach($this->users as $user) { foreach($user->getTags() as $tag) { $tagId = $tag->getId(); if(false === in_array($tagId, $ids, true)) { $ids[] = $tagId; } } } return $ids; 

$userToTags = function(User $user): array { return $user->getTags(); }; $tagToId = function(Tag $tag): int { return $tag->getId(); }; return array_unique(array_map($tagToId, array_merge( ...array_map($userToTags, $this->users) ))); 

$userToTags = function(User $user): array { return $user->getTags(); }; $tagToId = function(Tag $tag): int { return $tag->getId(); }; return $this->users ->flatMap($userToTags) ->map($tagToId) ->unique(); 

accidental accumulators 

$points = 0; foreach($this->users as $user) { $points += $user->getPoints(); } return $points; 

$points = 0; foreach($this->users as $user) { $points += $user->getPoints(); } return $points; 

$addPoints = function(int $state, User $user): int { return $state + $user->getPoints(); }; return array_reduce($this->users, $addPoints, 0); 

$addPoints = function(int $state, User $user): int { return $state + $user->getPoints(); }; return $this->users ->reduce($addPoints, 0); 

combined 

$isEnabled = function(User $u): bool { return !$u->isDisabled(); }; $isVisible = function(User $user): bool { return !$u->isHidden(); }; $userToPoints = function(User $user): int { return $user->getPoints(); }; $addPoints = function(int $st, User $u): int { return $st + $u->getPoints(); }; return $this->users ->filter($isEnabled) ->filter($isVisible) ->map($userToPoints) ->reduce($addPoints, 0); 

$isEnabled = function(User $u): bool { return !$u->isDisabled(); }; $isVisible = function(User $user): bool { return !$u->isHidden(); }; $userToPoints = function(User $user): int { return $user->getPoints(); }; $addPoints = function(int $st, User $u): int { return $st + $u->getPoints(); }; return $this->users ->filter($isEnabled) ->filter($isVisible) ->map($userToPoints) ->reduce($addPoints, 0); 

level 2: components 

request lifecycle 

entry | input → request routing | request → route controller | controller → response events | request → request | response → response forms | data → mapping validation | data → violations 

$response = controller(route($request)); 

object graph serialization 

objects → normalization → formatting → data data → parsing → hydration → objects 

$json = format(normalize($user)) $user = hydrate(parse($json)) 

$normalizers = new NormalizerContainer(); $normalizers->add(User::class, function(User $u) { return [ 'id' => $u->getId(), 'email' => $u->getEmail(), ]; }); 

$hydrators = new HydratorContainer(); $hydrators->add(User::class, function(array $data) { return new User($data['id'], $data['email']); }); 

$formats = new FormatContainer(); $formats->add('json', new JsonFormat()); 

$s = new Serializard($normalizers, $hydrators, $formats); $user = new User(1337, '[email protected]'); $json = $s->serialize($user, 'json'); $user = $s->unserialize($json, 'json', User::class); 

shortcode processing 

This is a [b]bold text[/b]. This is a bold text. 

string → parse → process → replace → string 

$string = replace(process(parse($input))) 

$handlers = new HandlerContainer(); $handlers->add('b', function(ShortcodeInterface $s) { return ''.$s->getContent().''; }); 

$parser = new RegexParser(); $parser = new WordpressParser(); $parser = new RegularParser(); 

$processor = new Processor($parser, $handlers); $text = 'This is a [b]bold text[/b].'; $result = $processor->process($text); 

level 3: systems 

modelling data flow 

applications microservices APIs 

challenges 

purpose 

comfort zone 

"real world" 

performance 

summary 

Slides: https://speakerdeck.com/thunderer/functional-approach-in-software-design Resources: https://github.com/thunderer/Shortcode https://github.com/thunderer/Serializard https://en.wikipedia.org/wiki/Functional_programming http://www.phptherightway.com/pages/Functional-Programming.html https://www.smashingmagazine.com/2014/07/dont-be-scared-of-functional-programming https://pragprog.com/magazines/2012-08/functional-thinking-for-the-imperative-mind http://lambdaconf.us/downloads/documents/lambdaconf_slfp.pdf Images: https://www.flickr.com/photos/kinematic/4078206226 (rocks) https://www.flickr.com/photos/kyetis/12506278675 (stones) https://www.flickr.com/photos/skyseeker/14404947216 (lightning) 

questions? 

how can I help? github /thunderer twitter @tmmx 

please rate the talk and leave feedback joind.in/talk/c0b77 

thanks! github /thunderer twitter @tmmx