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(Re)discovering the SPL

Joshua Thijssen
October 13, 2014
260

(Re)discovering the SPL

Joshua Thijssen

October 13, 2014
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  1. 2 Joshua Thijssen Freelance consultant and trainer @ TechAdemy Founder

    of TechAnalyze.io Founder of the Dutch Web Alliance Blog: http://adayinthelifeof.nl Email: [email protected] Twitter: @jaytaph
  2. 7

  3. 8

  4. 9

  5. 14

  6. ➡ Traversable cannot be implemented* ➡ Traversable can be detected

    (instanceof). ➡ foreach() detects traversable interfaces and does magic things. 14
  7. Iterator extends Traversable { /* Methods */ abstract public mixed

    current ( void ) abstract public scalar key ( void ) abstract public void next ( void ) abstract public void rewind ( void ) abstract public boolean valid ( void ) } 17 Iterator interface:
  8. 18

  9. 1 $dir = opendir("."); 2 while (($file = readdir($dir)) !==

    false) { 3 4 # Business logic happens here 5 print "file: $file\n"; 6 7 } 19
  10. 1 $dir = opendir("."); 2 while (($file = readdir($dir)) !==

    false) { 3 4 # hack: filter only mp3 files 5 if (! preg_match('|\.mp3$|i', $file)) { 6 continue; 7 } 8 9 # Business logic happens here 10 print "file: $file\n"; 11 } 20
  11. ➡ Filter all MP3 and all JPG files. ➡ Filter

    all MP3 files that are larger than 6MB. 21
  12. ➡ Filter all MP3 and all JPG files. ➡ Filter

    all MP3 files that are larger than 6MB. ➡ Do not filter at all. 21
  13. ➡ Filter all MP3 and all JPG files. ➡ Filter

    all MP3 files that are larger than 6MB. ➡ Do not filter at all. ➡ Search sub-directories as well. 21
  14. ➡ Filter all MP3 and all JPG files. ➡ Filter

    all MP3 files that are larger than 6MB. ➡ Do not filter at all. ➡ Search sub-directories as well. ➡ Search multiple directories. 21
  15. 22

  16. ➡ How to test? (we can’t) ➡ How to maintain?

    (we can’t) ➡ How to reuse? (we can’t) 22
  17. 1 $it = new DirectoryIterator("."); 2 foreach ($it as $fi)

    { 3 print "File: ".$fi->getPathname()."\n"; 4 } 23
  18. 1 $it = new DirectoryIterator("."); 2 $it2 = new RegexIterator($it,

    "/\.mp3$/i"); 3 foreach ($it2 as $fi) { 4 print "File: ".$fi->getPathname()."\n"; 5 } 24
  19. 1 $it = new DirectoryIterator("."); 2 $it2 = new RegexIterator($it,

    "/\.mp3$/i"); 3 $it3 = new FilesizeIterator($it2, 0, 6 * 1024 * 1024); 4 $it4 = new LimitIterator($it3, 10, 5); 5 6 foreach ($it4 as $fi) { 7 print "File: ".$fi->getPathname()."\n"; 8 } 25
  20. 1 $it = new DirectoryIterator("."); 2 $it2 = new RegexIterator($it,

    "/\.mp3$/i"); 3 $it3 = new FilesizeIterator($it2, 0, 6 * 1024 * 1024); 4 $it4 = new LimitIterator($it3, 10, 5); 5 6 foreach ($it4 as $fi) { 7 print "File: ".$fi->getPathname()."\n"; 8 } 25
  21. 26

  22. ✓ Reusable We can use iterators where ever we want.

    ✓ Testable Iterators can be tested separately. 26
  23. ✓ Reusable We can use iterators where ever we want.

    ✓ Testable Iterators can be tested separately. ✓ Maintainable No need to adapt our business logic. 26
  24. 1 class myIterator implements \Iterator { 2 /* ... */

    3 } 4 5 $a = array(1, 2, 3); 6 $it = new myIterator($a); 7 8 print count($it); 28
  25. 1 class myIterator implements \Iterator { 2 /* ... */

    3 } 4 5 $a = array(1, 2, 3); 6 $it = new myIterator($a); 7 8 print count($it); 1 28
  26. 1 class myCountableIterator extends myIterator implements Countable { 2 function

    count() { 3 return count($this->_elements); 4 } 5 } 6 7 $a = array(1, 2, 3, 4, 5); 8 $it = new myCountableIterator($a); 9 10 print count($it); 29
  27. 1 class myCountableIterator extends myIterator implements Countable { 2 function

    count() { 3 return count($this->_elements); 4 } 5 } 6 7 $a = array(1, 2, 3, 4, 5); 8 $it = new myCountableIterator($a); 9 10 print count($it); 5 29
  28. 1 class myCountableIterator extends myIterator implements Countable { 2 function

    count() { 3 return count($this->_arr); 4 } 5 } 6 7 $a = array(1, 2, 3, 4, 5); 8 $it = new myCountableIterator($a); 9 $it2 = new limitIterator($it, 0, 3); 10 11 print count($it2); 30
  29. 1 class myCountableIterator extends myIterator implements Countable { 2 function

    count() { 3 return count($this->_arr); 4 } 5 } 6 7 $a = array(1, 2, 3, 4, 5); 8 $it = new myCountableIterator($a); 9 $it2 = new limitIterator($it, 0, 3); 10 11 print count($it2); 1 30
  30. SPL Iterators ➡ AppendIterator ➡ ArrayIterator ➡ CachingIterator ➡ CallbackFilterIterator

    ➡ DirectoryIterator ➡ EmptyIterator ➡ FilesystemIterator ➡ FilterIterator ➡ GlobIterator ➡ InfiniteIterator ➡ IteratorIterator ➡ LimitIterator ➡ MultipleIterator ➡ NoRewindIterator ➡ ParentIterator ➡ RecursiveArrayIterator ➡ RecursiveCachingIterator ➡ RecursiveCallbackFilterIterator ➡ RecursiveDirectoryIterator ➡ RecursiveFilterIterator ➡ RecursiveIteratorIterator ➡ RecursiveRegexIterator ➡ RecursiveTreeIterator ➡ RegexIterator ➡ SimpleXMLIterator 32
  31. 34

  32. 35

  33. 38 1 $it = new myIterator(); 2 if ($it instanceof

    \IteratorAggregate) { 3 $it = $it->getIterator(); 4 } 5 $it2 = new \LimitIterator($it, 5, 10);
  34. 39 1 $it = new myIterator(); 2 $it2 = new

    \IteratorIterator($it); 3 $it3 = new \LimitIterator($it2, 5, 10);
  35. 41 1 $it = new ArrayIterator( 2 array("foo", "bar", array("qux",

    "wox"), "baz")); 3 4 foreach ($it as $v) { 5 print $v . "\n"; 6 }
  36. 41 1 $it = new ArrayIterator( 2 array("foo", "bar", array("qux",

    "wox"), "baz")); 3 4 foreach ($it as $v) { 5 print $v . "\n"; 6 } foo bar Array baz
  37. 42 1 $it = new RecursiveArrayIterator( 2 array("foo", "bar", array("qux",

    "wox"), "baz")); 3 4 foreach ($it as $v) { 5 print $v . "\n"; 6 }
  38. 42 1 $it = new RecursiveArrayIterator( 2 array("foo", "bar", array("qux",

    "wox"), "baz")); 3 4 foreach ($it as $v) { 5 print $v . "\n"; 6 } foo bar Array baz
  39. 43 1 $it = new RecursiveArrayIterator( 2 array("foo", "bar", array("qux",

    "wox"), "baz")); 3 $it2 = new RecursiveIteratorIterator($it); 4 5 foreach ($it2 as $v) { 6 print $v . "\n"; 7 }
  40. 43 1 $it = new RecursiveArrayIterator( 2 array("foo", "bar", array("qux",

    "wox"), "baz")); 3 $it2 = new RecursiveIteratorIterator($it); 4 5 foreach ($it2 as $v) { 6 print $v . "\n"; 7 } foo bar qux wox baz
  41. ➡ Enables recursivity ➡ Is a filter iterator (does not

    necessarily return all the elements) ➡ Filters through a callback function. 46
  42. ➡ It has “quirks” that are easily solvable (but breaks

    BC) ➡ Documentation is not always up to date. ➡ Naming is VERY confusing (caching iterator, recursiveIterator, seekableIterator) ➡ But the iterators are worth it! 48
  43. 50 ➡ SplDoublyLinkedList ➡ SplStack ➡ SplQueue ➡ SplHeap ➡

    SplMinHeap ➡ SplMaxHeap ➡ SplPriorityQueue ➡ SplFixedArray ➡ SplObjectStorage
  44. 51 ➡ Every data structure has its strength and weaknesses.

    ➡ Big-Oh O(1), O(n), O(log n) etc... ➡ Balance between time (CPU) and space (memory) ➡ PHP arrays are quite good! ➡ But sometimes other data structures are better.
  45. 54

  46. 57

  47. 60 ➡ Use wisely: ➡ Don’t use SplStack / SplQueue

    for random reads. ➡ Don’t use FixedArrays when you need speed boosts.
  48. ➡ BadFunctionCallException ➡ BadMethodCallException ➡ DomainException ➡ InvalidArgumentException ➡ LengthException

    ➡ LogicException ➡ OutOfBoundsException ➡ OutOfRangeException ➡ OverflowException ➡ RangeException ➡ RuntimeException ➡ UnderflowException ➡ UnexpectedValueException 62
  49. ➡ BadFunctionCallException ➡ BadMethodCallException ➡ DomainException ➡ InvalidArgumentException ➡ LengthException

    ➡ OutOfRangeException 63 Logic Exceptions Runtime Exceptions ➡ OutOfBoundsException ➡ OverflowException ➡ RangeException ➡ UnderflowException ➡ UnexpectedValueException
  50. 64 1 function foo($str) { 2 if ($str == "The

    Spanish Inquisition") { 3 throw new \UnexpectedValueException("Nobody expects ".$str); 4 } 5 /* ... */ 6 }
  51. 65 1 function foo($str) { 2 if ($str == "The

    Spanish Inquisition") { 3 throw new \InvalidArgumentException("Nobody expects ".$str); 4 } 5 /* ... */ 6 } Logic, not runtime
  52. 66 1 function foo($str) { 2 if ($str == "The

    Spanish Inquisition") { 3 /* logic */ 4 throw new \InvalidArgumentException("Nobody expects ".$str); 5 } 6 7 try { 8 $this->getDatabase()->saveRecord($str); 9 } catch (\RuntimeException $e) { 10 /* We could try again here */ 11 } catch (\Exception $e) { 12 /* Sorry, something else occurred. */ 13 } 14 }
  53. 75 1 $a = array("foo", "bar"); 2 $b = $a;

    3 $b[] = "baz"; 4 5 print_r ($a); 6 print_r ($b);
  54. 75 1 $a = array("foo", "bar"); 2 $b = $a;

    3 $b[] = "baz"; 4 5 print_r ($a); 6 print_r ($b); Array ( [0] => foo [1] => bar ) Array ( [0] => foo [1] => bar [2] => baz )
  55. 76 1 $a = new ArrayObject(); 2 $a[] = "foo";

    3 $a[] = "bar"; 4 5 $b = $a; 6 $b[] = "baz"; 7 8 print_r (iterator_to_array($a)); 9 print_r (iterator_to_array($b));
  56. 76 1 $a = new ArrayObject(); 2 $a[] = "foo";

    3 $a[] = "bar"; 4 5 $b = $a; 6 $b[] = "baz"; 7 8 print_r (iterator_to_array($a)); 9 print_r (iterator_to_array($b)); Array ( [0] => foo [1] => bar [2] => baz ) Array ( [0] => foo [1] => bar [2] => baz )
  57. ➡ Not all that bad! ➡ Makes heavy use of

    iterators ➡ Exceptions are ok ➡ Too many new \Exceptions() (129) ➡ Datastructures not really 78
  58. 80 ➡ The (first and only) book about the SPL.

    ➡ Written by me (so you know it’s good :P) ➡ Fixes the documentation problem of the SPL (or a wobbly table)
  59. 81

  60. ➡ Adaption of the SPL will only happen when developers

    can become familiar with it. ➡ There is currently no real way to familiarize yourself with the SPL. 81
  61. 84 Find me on twitter: @jaytaph Find me for development

    and training: www.noxlogic.nl Find me on email: [email protected] Find me for blogs: www.adayinthelifeof.nl Symfony2 Webinar