1. perlDreamer Consulting, LLC1 Common WebGUI Programming Mistakes

2. perlDreamer Consulting, LLC2 Common WebGUI Programming Mistakes

3. perlDreamer Consulting, LLC3 Common WebGUI Programming Mistakes and Things that Are Bad

4. perlDreamer Consulting, LLC4 Common WebGUI Programming Mistakes and Things that Are Bad and Stuff I Don't Like

5. perlDreamer Consulting, LLC5 What's up? ● Some of these aren't "mistakes" – They're silly. – Dangerous. – Needless. – Just my opinion ● Short, on-topic discussions of opinion are encouraged. ● Keep an eye on the clock.

6. perlDreamer Consulting, LLC6 Format for the talk ● I'm going to throw up code and coding practices. – For the most part, they're anonymous. ● If you think you know the mistake, please raise your hand. ● Bonus points for not using a reference. ● PLEASE DO NOT BLURT OUT ANSWERS.

7. perlDreamer Consulting, LLC7 What's up? ● If seeing your code up here is going to – Get your goat. – Make you mad. – Make you embarrassed. ● You might want to leave now...

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11. perlDreamer Consulting, LLC11 ● Until 7.5.11, virtually all class methods in WebGUI required a session variable. Missing session variable

12. perlDreamer Consulting, LLC12 ● WebGUI::Shop::Address takes a WebGUI::Shop::AddressBook. ● WebGUI::Shop::CartItem takes a WebGUI::Shop::Cart. ● WebGUI::Shop::TransactionItem takes a WebGUI::Shop::Transaction. Constructors that don't take a Session object

13. perlDreamer Consulting, LLC13 ● General pattern is WebGUI::Object takes a WebGUI::Container. ● When the Object wants to access a session object, it does it through it's parent, the Container. Constructors that don't take a Session object

14. perlDreamer Consulting, LLC14 ● Several recently made methods check for a session variable or container object passed to constructors. – Constructors in WebGUI::Shop – WebGUI::Asset->newPending ● They either return undef, croak, or throw an exception. Missing session variable

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16. perlDreamer Consulting, LLC16 ● i18n really isn't an object, it's a gateway. ● Call it as a subroutine and give it something useful as a first argument... – Like a session variable ● WebGUI::Session does not have a session method. – $self->session->log->warn won't work Abusing object methods

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18. perlDreamer Consulting, LLC18 Failing to check a constructor ● Most constructors return undef when they fail, instead of throwing an exception. ● Be sure to check that you got returned an object before using it. – "Can't call method purge on an undefined value" ● New constructors, newPending, will throw an exception.

19. perlDreamer Consulting, LLC19 Check constructor

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21. perlDreamer Consulting, LLC21 Long running objects ● What happened to the Asset's version control status? ● $versionTag->commit creates a new copy of the Asset and updates the status in the database. ● But $asset still thinks it is 'pending'. ● Calling $asset->update updates the database with its own status, not the one from the database.

22. perlDreamer Consulting, LLC22 How to avoid this

23. perlDreamer Consulting, LLC23 How to avoid this #2

24. perlDreamer Consulting, LLC24 ● WebGUI::Asset->new($session); ● WebGUI::Group->new($session); ● WebGUI::User->new($session); ● WebGUI::Storage->new($session);

25. perlDreamer Consulting, LLC25 Constructors vs Instanciators ● WebGUI::Asset->new($session); – Find an existing asset ● WebGUI::Group->new($session); – Build a new group from scratch. ● WebGUI::User->new($session, $userId); – Build a new user, only if $userId eq 'new' ● WebGUI::Storage does not have a new method. – use create for new objects – use find for existing objects

26. perlDreamer Consulting, LLC26 Constructors vs Instanciators ● Most recently added code uses – create for accessing existing objects. – new for contructing new objects from scratch. ● The worst offender is Asset.pm with – new, newPending – newByUrl, newByPropertyHashRef – addChild, newByDynamicClass

27. perlDreamer Consulting, LLC27 Goal: Get the name of a user by ID.

28. perlDreamer Consulting, LLC28 Learn the WebGUI API ● There's nothing technically wrong with this code, but it's still a mistake. ● There's no need to open a session object to get a user object. – Create a user object instead.

29. perlDreamer Consulting, LLC29 Goal: Get the name of a user by ID.

30. perlDreamer Consulting, LLC30 The Real Lesson ● The person who wrote this code asked how to get the name of a user from the session variable. ● But that wasn't what they wanted to know. ● When asking questions, give context. ● "This is what I want to do, this is what I have, here's how I'm trying to do it..."

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32. perlDreamer Consulting, LLC32 Learn Perl ● That snippet of perl code reimplements perl's exists function, but much more slowly. ● Invest time in: – Keeping abreast of changes in Perl. – New modules on CPAN. – Learning what's new in MySQL –...and JavaScript, and YUI. – What's new in CMSes and other web frameworks.

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34. perlDreamer Consulting, LLC34 Beware IRCers bearing gifts ● The person who wrote this code got "help" from someone in IRC. – /me ● They didn't know the "shorthand" of dropping WebGUI:: ● The common mistake: Laziness. – The old dev saved 5 seconds. – The new dev didn't double check.

35. perlDreamer Consulting, LLC35 IRC tips ● Search the forums and bug list before asking questions on IRC. ● Grep through the tests and WebGUI code for examples. ● Never blindly paste code from IRC without double checking it first. ● Don't ask to ask, just ask it. – Then be patient.

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37. perlDreamer Consulting, LLC37 Asset vs VersionTag Commit ● Committing an asset will change its status and state. ● But it won't do anything for the version tag that was automatically created for you. ● That tag will just be sitting around – and confusing the users.

38. perlDreamer Consulting, LLC38 Make a CS with RSS

39. perlDreamer Consulting, LLC39 Make a CS with RSS #2

40. perlDreamer Consulting, LLC40 How do you make an CS with RSS? ● RSS in WebGUI is an Asset. ● It requires multiple inheritance, which is handled by the NEXT module. ● It only works when Assets are added through the GUI. ● Programmatic calls to new*, update, addChild, etc. are completely ignored. ● It is total crap.

41. perlDreamer Consulting, LLC41 Make a CS with RSS, really

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43. perlDreamer Consulting, LLC43 OO Inheritance ● We have a base class and a child class. ● But the overridden method has different parameters from the parent. – I guess that's one way to make sure it gets overridden.

44. perlDreamer Consulting, LLC44 Template Variables

45. perlDreamer Consulting, LLC45 HTML::Template

46. perlDreamer Consulting, LLC46 Outputs

47. perlDreamer Consulting, LLC47 HTML::Template and undef ● If a variable in a loop is undef... ● And outside the loop a variable with the same name exists ● Then the undef is replaced with the value of the variable from outside the loop. ● '' is okay, this only happens with undef ● Doug wrote a fix for this bug six months ago. – Still waiting for it to be applied.

48. perlDreamer Consulting, LLC48 Buried inside WebGUI::Asset::Wobject::Calendar

49. perlDreamer Consulting, LLC49 viewWeek reorders events? ● What's up with that? ● Why not write www_reorderEvents and then call viewWeek at the end of that? ● Use encapsulation and separation of interests.

50. perlDreamer Consulting, LLC50 Want to “enhance” the Product ● If you modify WebGUI/Asset/Sku/Product.pm, the customer will need to do manual upgrades forever. ● What else can you do?

51. perlDreamer Consulting, LLC51 Copy it all. ● You build WebGUI/Asset/Sku/MyProduct.pm ● Benefits: – Safer upgrades. ● Penalties: – Manual merge for features and bugfixes in any code.

52. perlDreamer Consulting, LLC52 Subclass Product.pm ● Build WebGUI/Asset/Sku/Product/My.pm – Override and add only the code you need. ● Benefits: – Safe upgrades. – Automatic bugfixes in non-overridden code. ● Penalties: – Manual merge for features and bugfixes in any overridden code.

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54. perlDreamer Consulting, LLC54 Non-existant JSON Array ● If there are no records, the “records” entry in the hash is never made into an array. ● YUI says this:

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56. perlDreamer Consulting, LLC56 Happy YUI ● Pagination labels. ● Nice message about having no data.

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59. perlDreamer Consulting, LLC59 Returning unsafe references ● Notice there are two places where references are returned. ● Each reference will allow the user to alter data inside of the object. – Stuff – Stow cache inside the session variable.

60. perlDreamer Consulting, LLC60 Returning unsafe references ● When the bug is tripped, it will be by a user of this code, and not the code itself. ● This makes the code VERY FRUSTRATINGLY HARD TO FIND!!! ● WebGUI is still full of these kinds of bugs. ● This last one is modeled off of the getGroups method in Groups – which has 100% test coverage

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66. perlDreamer Consulting, LLC66 The biggest mistake ● Used emacs.

67. perlDreamer Consulting, LLC67 Emacs vs vim vs butterflies

68. perlDreamer Consulting, LLC68 SVN mistakes ● Did not use a commit message. – How will others (or you) figure out what this commit was for? ● Always use a brief, descriptive commit message. – "Time tracker changes" – "clean up test warnings" – "fix a potential future syntax error"

69. perlDreamer Consulting, LLC69 SVN mistakes ● Committed everything, not just the changes to Asset.pm. – Related to a bad commit message. – The ideal SVN workflow has small, atomic commits.

70. perlDreamer Consulting, LLC70 Procedural Mistakes ● Didn't run a syntax check. ● Didn't start (or restart) Apache. – So they didn't check their code in a browser. ● Didn't rerun the test suite. ● Didn't add new tests to check their code. – Not always possible, but more than you might think...