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:
| 1 | <?php  | 
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| 11 | trait ManagesContacts  | 
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| 12 | { | 
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| 13 | /**  | 
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| 14 | * Get all contacts.  | 
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| 15 | *  | 
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| 16 | * @return array  | 
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| 17 | */  | 
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| 18 | public function contacts()  | 
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| 26 | |||
| 27 | /**  | 
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| 28 | * Find contact by email.  | 
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| 29 | *  | 
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| 30 | * @param string $email  | 
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| 31 | *  | 
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| 32 | * @return Contact|null  | 
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| 33 | */  | 
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| 34 | public function findContact($email)  | 
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| 44 | |||
| 45 | /**  | 
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| 46 | * Find contact by ID.  | 
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| 47 | *  | 
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| 48 | * @param int $id  | 
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| 49 | *  | 
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| 50 | * @return Contact|null  | 
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| 51 | */  | 
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| 52 | public function findContactById($id)  | 
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| 57 | |||
| 58 | /**  | 
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| 59 | * Create new contact.  | 
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| 60 | *  | 
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| 61 | * @param string $email  | 
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| 62 | * @param string $firstName  | 
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| 63 | * @param string $lastName  | 
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| 64 | * @param int|null $orgid  | 
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| 65 | *  | 
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| 66 | * @return Contact|null  | 
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| 67 | */  | 
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| 68 | public function createContact($email, $firstName, $lastName, $orgid = null)  | 
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| 77 | |||
| 78 | /**  | 
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| 79 | * Find or create a contact.  | 
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| 80 | *  | 
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| 81 | * @param string $email  | 
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| 82 | * @param string $firstName  | 
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| 83 | * @param string $lastName  | 
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| 84 | * @param int|null $orgid  | 
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| 85 | *  | 
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| 86 | * @return Contact  | 
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| 87 | */  | 
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| 88 | public function findOrCreateContact($email, $firstName, $lastName, $orgid = null)  | 
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| 98 | |||
| 99 | /**  | 
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| 100 | * Updates a contact.  | 
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| 101 | *  | 
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| 102 | * @param Contact|int|string $id  | 
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| 103 | * @param string|null $email  | 
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| 104 | * @param string|null $firstName  | 
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| 105 | * @param string|null $lastName  | 
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| 106 | * @param null $orgid  | 
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| 107 | *  | 
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| 108 | * @return Contact|null  | 
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| 109 | */  | 
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| 110 | public function updateContact($id, $email, $firstName, $lastName, $orgid = null)  | 
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| 118 | |||
| 119 | /**  | 
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| 120 | * Deletes a contact.  | 
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| 121 | *  | 
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| 122 | * @param Contact|int|string $contact  | 
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| 123 | */  | 
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| 124 | public function deleteContact($contact)  | 
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| 128 | |||
| 129 | /**  | 
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| 130 | * Get all automations of a contact.  | 
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| 131 | *  | 
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| 132 | * @param \TestMonitor\ActiveCampaign\Resources\Contact $contact  | 
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| 133 | *  | 
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| 134 | * @return array  | 
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| 135 | */  | 
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| 136 | public function contactAutomations(Contact $contact)  | 
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| 144 | |||
| 145 | /**  | 
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| 146 | * Get all tags of a contact.  | 
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| 147 | *  | 
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| 148 | * @param \TestMonitor\ActiveCampaign\Resources\Contact $contact  | 
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| 149 | *  | 
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| 150 | * @return array  | 
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| 151 | */  | 
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| 152 | public function contactTags(Contact $contact)  | 
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| 160 | |||
| 161 | /**  | 
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| 162 | * Removing a automation from a contact.  | 
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| 163 | *  | 
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| 164 | * @param \TestMonitor\ActiveCampaign\Resources\Contact $contact  | 
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| 165 | * @param \TestMonitor\ActiveCampaign\Resources\Automation $automation  | 
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| 166 | */  | 
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| 167 | View Code Duplication | public function removeAutomationFromContact(Contact $contact, Automation $automation)  | 
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| 181 | |||
| 182 | /**  | 
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| 183 | * Removing all automations from a contact.  | 
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| 184 | *  | 
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| 185 | * @param \TestMonitor\ActiveCampaign\Resources\Contact $contact  | 
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| 186 | */  | 
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| 187 | public function removeAllAutomationsFromContact(Contact $contact)  | 
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| 195 | |||
| 196 | /**  | 
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| 197 | * Removing a tag from a contact.  | 
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| 198 | *  | 
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| 199 | * @param \TestMonitor\ActiveCampaign\Resources\Contact $contact  | 
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| 200 | * @param \TestMonitor\ActiveCampaign\Resources\Tag $tag  | 
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| 201 | */  | 
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| 202 | View Code Duplication | public function removeTagFromContact(Contact $contact, Tag $tag)  | 
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| 216 | |||
| 217 | /**  | 
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| 218 | * Determines the contact ID.  | 
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| 219 | *  | 
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| 220 | * @param Contact|int|string $contact  | 
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| 221 | */  | 
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| 222 | protected function getContactId($contact)  | 
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| 234 | }  | 
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| 235 | 
This check looks for methods that are used by a trait but not required by it.
To illustrate, let’s look at the following code example
The trait
Idableprovides a methodequalsIdthat in turn relies on the methodgetId(). If this method does not exist on a class mixing in this trait, the method will fail.Adding the
getId()as an abstract method to the trait will make sure it is available.