Duplicate code is one of the most pungent code smells. A rule that is often used is to re-structure code once it is duplicated in three or more places.
Common duplication problems, and corresponding solutions are:
Complex classes like BlogPost often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use BlogPost, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 18 | class BlogPost extends Page  | 
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| 19 | { | 
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| 20 | /**  | 
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| 21 | * Same as above, but for list of users that can be  | 
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| 22 | * given credit in the author field for blog posts  | 
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| 23 | * @var string|bool false or group code  | 
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| 24 | */  | 
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| 25 | private static $restrict_authors_to_group = false;  | 
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| 26 | |||
| 27 | /**  | 
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| 28 | * @var array  | 
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| 29 | */  | 
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| 30 | private static $db = array(  | 
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| 31 | 'PublishDate' => 'SS_Datetime',  | 
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| 32 | 'AuthorNames' => 'Varchar(1024)',  | 
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| 33 | 'Summary' => 'HTMLText',  | 
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| 34 | );  | 
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| 35 | |||
| 36 | /**  | 
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| 37 | * @var array  | 
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| 38 | */  | 
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| 39 | private static $has_one = array(  | 
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| 40 | 'FeaturedImage' => 'Image',  | 
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| 41 | );  | 
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| 42 | |||
| 43 | /**  | 
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| 44 | * @var array  | 
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| 45 | */  | 
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| 46 | private static $many_many = array(  | 
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| 47 | 'Categories' => 'BlogCategory',  | 
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| 48 | 'Tags' => 'BlogTag',  | 
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| 49 | 'Authors' => 'Member',  | 
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| 50 | );  | 
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| 51 | |||
| 52 | /**  | 
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| 53 | * @var array  | 
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| 54 | */  | 
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| 55 | private static $defaults = array(  | 
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| 56 | 'ShowInMenus' => false,  | 
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| 57 | 'InheritSideBar' => true,  | 
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| 58 | 'ProvideComments' => true,  | 
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| 59 | );  | 
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| 60 | |||
| 61 | /**  | 
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| 62 | * @var array  | 
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| 63 | */  | 
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| 64 | private static $extensions = array(  | 
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| 65 | 'BlogPostFilter',  | 
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| 66 | );  | 
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| 67 | |||
| 68 | /**  | 
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| 69 | * @var array  | 
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| 70 | */  | 
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| 71 | private static $searchable_fields = array(  | 
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| 72 | 'Title',  | 
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| 73 | );  | 
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| 74 | |||
| 75 | /**  | 
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| 76 | * @var array  | 
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| 77 | */  | 
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| 78 | private static $summary_fields = array(  | 
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| 79 | 'Title',  | 
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| 80 | );  | 
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| 81 | |||
| 82 | /**  | 
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| 83 | * @var array  | 
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| 84 | */  | 
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| 85 | private static $casting = array(  | 
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| 86 | 'Excerpt' => 'Text',  | 
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| 87 | );  | 
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| 88 | |||
| 89 | /**  | 
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| 90 | * @var array  | 
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| 91 | */  | 
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| 92 | private static $allowed_children = array();  | 
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| 93 | |||
| 94 | /**  | 
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| 95 | * The default sorting lists BlogPosts with an empty PublishDate at the top.  | 
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| 96 | *  | 
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| 97 | * @var string  | 
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| 98 | */  | 
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| 99 | private static $default_sort = '"PublishDate" IS NULL DESC, "PublishDate" DESC';  | 
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| 100 | |||
| 101 | /**  | 
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| 102 | * @var bool  | 
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| 103 | */  | 
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| 104 | private static $can_be_root = false;  | 
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| 105 | |||
| 106 | /**  | 
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| 107 | * This will display or hide the current class from the SiteTree. This variable can be  | 
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| 108 | * configured using YAML.  | 
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| 109 | *  | 
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| 110 | * @var bool  | 
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| 111 | */  | 
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| 112 | private static $show_in_sitetree = false;  | 
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| 113 | |||
| 114 | /**  | 
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| 115 | * Determine the role of the given member.  | 
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| 116 | *  | 
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| 117 | * Call be called via template to determine the current user.  | 
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| 118 | *  | 
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| 119 | * @example "Hello $RoleOf($CurrentMember.ID)"  | 
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| 120 | *  | 
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| 121 | * @param null|int|Member $member  | 
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| 122 | *  | 
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| 123 | * @return null|string  | 
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| 124 | */  | 
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| 125 | public function RoleOf($member = null)  | 
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| 145 | |||
| 146 | /**  | 
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| 147 | * Determine if the given member is an author of this post.  | 
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| 148 | *  | 
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| 149 | * @param null|Member $member  | 
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| 150 | *  | 
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| 151 | * @return bool  | 
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| 152 | */  | 
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| 153 | View Code Duplication | public function isAuthor($member = null)  | 
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| 167 | |||
| 168 | /**  | 
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| 169 |      * {@inheritdoc} | 
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| 170 | */  | 
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| 171 | public function getCMSFields()  | 
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| 289 | |||
| 290 | /**  | 
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| 291 | * Gets the list of author candidates to be assigned as authors of this blog post.  | 
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| 292 | *  | 
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| 293 | * @return SS_List  | 
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| 294 | */  | 
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| 295 | public function getCandidateAuthors()  | 
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| 305 | |||
| 306 | /**  | 
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| 307 | * Determine if this user can edit the authors list.  | 
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| 308 | *  | 
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| 309 | * @param null|int|Member $member  | 
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| 310 | *  | 
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| 311 | * @return bool  | 
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| 312 | */  | 
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| 313 | public function canEditAuthors($member = null)  | 
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| 337 | |||
| 338 | /**  | 
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| 339 | * @param null|int|Member $member  | 
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| 340 | *  | 
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| 341 | * @return null|Member  | 
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| 342 | */  | 
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| 343 | View Code Duplication | protected function getMember($member = null)  | 
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| 355 | |||
| 356 | /**  | 
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| 357 | * Determine whether user can create new categories.  | 
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| 358 | *  | 
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| 359 | * @param null|int|Member $member  | 
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| 360 | *  | 
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| 361 | * @return bool  | 
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| 362 | */  | 
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| 363 | View Code Duplication | public function canCreateCategories($member = null)  | 
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| 379 | |||
| 380 | /**  | 
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| 381 | * Determine whether user can create new tags.  | 
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| 382 | *  | 
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| 383 | * @param null|int|Member $member  | 
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| 384 | *  | 
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| 385 | * @return bool  | 
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| 386 | */  | 
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| 387 | View Code Duplication | public function canCreateTags($member = null)  | 
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| 407 | |||
| 408 | /**  | 
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| 409 |      * {@inheritdoc} | 
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| 410 | *  | 
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| 411 | * Update the PublishDate to now if the BlogPost would otherwise be published without a date.  | 
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| 412 | */  | 
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| 413 | public function onBeforePublish()  | 
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| 425 | |||
| 426 | /**  | 
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| 427 |      * {@inheritdoc} | 
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| 428 | *  | 
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| 429 | * Sets blog relationship on all categories and tags assigned to this post.  | 
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| 430 | */  | 
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| 431 | public function onAfterWrite()  | 
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| 451 | |||
| 452 | /**  | 
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| 453 |      * {@inheritdoc} | 
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| 454 | */  | 
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| 455 | public function canView($member = null)  | 
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| 477 | |||
| 478 | /**  | 
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| 479 |      * {@inheritdoc} | 
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| 480 | */  | 
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| 481 | public function canPublish($member = null)  | 
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| 513 | |||
| 514 | /**  | 
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| 515 |      * {@inheritdoc} | 
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| 516 | */  | 
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| 517 | public function canEdit($member = null)  | 
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| 541 | |||
| 542 | /**  | 
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| 543 | * Returns the post excerpt.  | 
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| 544 | *  | 
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| 545 | * @param int $wordsToDisplay  | 
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| 546 | *  | 
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| 547 | * @return string  | 
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| 548 | */  | 
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| 549 | public function Excerpt($wordsToDisplay = 30)  | 
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| 558 | |||
| 559 | /**  | 
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| 560 | * Returns a monthly archive link for the current blog post.  | 
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| 561 | *  | 
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| 562 | * @param string $type  | 
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| 563 | *  | 
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| 564 | * @return string  | 
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| 565 | */  | 
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| 566 | public function getMonthlyArchiveLink($type = 'day')  | 
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| 588 | |||
| 589 | /**  | 
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| 590 | * Returns a yearly archive link for the current blog post.  | 
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| 591 | *  | 
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| 592 | * @return string  | 
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| 593 | */  | 
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| 594 | public function getYearlyArchiveLink()  | 
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| 603 | |||
| 604 | /**  | 
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| 605 | * Resolves static and dynamic authors linked to this post.  | 
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| 606 | *  | 
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| 607 | * @return ArrayList  | 
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| 608 | */  | 
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| 609 | public function getCredits()  | 
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| 618 | |||
| 619 | /**  | 
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| 620 | * Resolves dynamic authors linked to this post.  | 
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| 621 | *  | 
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| 622 | * @return ArrayList  | 
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| 623 | */  | 
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| 624 | protected function getDynamicCredits()  | 
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| 650 | |||
| 651 | /**  | 
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| 652 | * Resolves static authors linked to this post.  | 
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| 653 | *  | 
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| 654 | * @return ArrayList  | 
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| 655 | */  | 
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| 656 | protected function getStaticCredits()  | 
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| 672 | |||
| 673 | /**  | 
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| 674 | * Sets the label for BlogPost.Title to 'Post Title' (Rather than 'Page name').  | 
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| 675 | *  | 
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| 676 | * @param bool $includeRelations  | 
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| 677 | *  | 
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| 678 | * @return array  | 
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| 679 | */  | 
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| 680 | public function fieldLabels($includeRelations = true)  | 
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| 688 | |||
| 689 | /**  | 
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| 690 |      * {@inheritdoc} | 
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| 691 | */  | 
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| 692 | protected function onBeforeWrite()  | 
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| 700 | }  | 
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| 701 | |||
| 709 | 
You can fix this by adding a namespace to your class:
When choosing a vendor namespace, try to pick something that is not too generic to avoid conflicts with other libraries.