Iterators

Iterators a super powerful tool that is part of the SPL.

Companion Code: https://github.com/jtyost2/LasVegas-PHP-Iterators

Transcript

1. Iterators:)A)Super)Powerful)Tool Jus$n&Yost • twi%er.com/jtyost2 • github.com/jtyost2 • h%ps:/ /speakerdeck.com/jtyost2/iterators
2. SPL$%$Standard$PHP$Library • Default)since)PHP)5.0 • Always)there)since)PHP)5.3 • Bunch)of)interfaces)and)classes)with)a)ton)of)useful)tools
3. SPL$contains 1. Common'Data'Structures:'(Stacks,'Linked'Lists,'Heaps,'Queues,' etc) 2. Excep?ons:'(InvalidArgument,'OutOfRange,'etc) 3. File'Handling'Classes 4. Some'Class'Methods 5. Interfaces:'Mostly'?ed'to'the'Iterators 6. Iterators
4. What%is%an%Iterator? In#object*oriented#computer#programming,#an#iterator#is#an#object# that#enables#a#programmer#to#traverse#a#container,#par8cularly#lists. —"From"Wikipedia"(h0ps://en.wikipedia.org/wiki/Iterator)
5. Thanks,(I(think? List%of%Stuff%+%Need%to%Loop%Through%It%=%Iterator
6. So#it's#a#foreach? • Sorta,(it's(a(foreach(but(be/er(and(more(awesome
7. So#what#does#a#Standard#foreach#look#like? $someArrayOfStuff = array(); foreach($someArrayOfStuff as $key => $value) { $someArrayOfStuff[$key] = mainpulateValue($value); } foreach($someArrayOfStuff as $key => $value) { displayStuff($value); } Pre$y&standard&pa$ern&in&PHP
8. Is#this#bad?
9. Maybe&not • Given'a'small'enough'set'of'inputs'and'only'looping'through' once'it's'probably'fine
10. Imagine(doing(some(manipula/on(mul/ple(/mes? $someDataInput = array(); foreach($someDataInput as $key => $data) { $someDataInput[$key] = manipulateTheData($data); } foreach($someDataInput as $key => $data) { $someDataInput[$key] = caclulateStatisticsOfManipulateData($data); } foreach($someDataInput as $key => $data) { displayData($data); }
11. This%can%get%long,%ugly%and%more%complicated • Also&really&slow&to&loop&through&your&whole&collec2on&of&data& mul2ple&2mes • We&really&want&to&loop&through&it&once
12. Iterators(are(the(solu,on Iterators(follow(a(basic(pa0ern: Think&the&normal&foreach&loop& foreach($obj as $key => $value) $iterator->rewind(); while ($iterator->valid()) { $iterator->current(); //$value $iterator->key(); //$key $iterator->next(); } Keep$this$pa*ern$in$mind.
13. Code We#have#some#data php ./basic/basic.php print
14. Code We#have#some#data#to#iterate#over#it php ./basic/basic.php
15. Code Throw&out&all&elements&where&the&name&is&less&than&10&chars&in& length php ./basic/basic.php
16. Code Want%to%turn%our%csv%into%an%indexed%array%(id%=>%x,%name%=>%y,...) php ./csv/basic.php
17. Code We#want#to#ensure#required#fields#are#set php ./csv/required.php
18. Code We#want#to#ensure#required#fields#are#set#and#name#is#less#than#10# chars#in#length php ./csv/required_and_length.php
19. Stack&iterators • The%real%power%of%iterators%comes%from%being%able%to%stack%them. • Think%a%stack%of%iterators%that%each%performs%a%dedicated%task • Then%apply%the%stack%as%you%need%for%a%set%of%objects
20. Stack&Iterators • One%stack%to%throw%out%bad%data%(FilterIterator) • One%stack%to%do%math%on%the%data%(ArrayIterator) • One%stack%to%calculate%based%upon%the%earlier%math%performed% (ArrayIterator)
21. Sum$it$up • Iterator(is(a(way(of(looping(through(a(set(of(data(and(doing(stuff( on(it • Way(more(powerful(that(a(basic(foreach(loop,(though(the( concept(is(similar • They(can(be(stacked(with(no("real"(hit(on(performance • Lets(you(do(way(more(than(you(could(with(a(simple(foreach( loop
22. Ques%ons? Jus$n&Yost • twi%er.com/jtyost2 • github.com/jtyost2 • h%ps:/ /speakerdeck.com/jtyost2/iterators