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:
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| 9 | trait HasClassTrait  | 
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| 10 | { | 
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| 11 | /**  | 
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| 12 | * @return $this  | 
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| 13 | */  | 
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| 14 | 5 | public function addClass()  | 
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| 29 | /**  | 
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| 30 | * @return $this  | 
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| 31 | */  | 
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| 32 | 1 | View Code Duplication | public function removeClass()  | 
            
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| 50 | /**  | 
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| 51 | * @param string $class  | 
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| 52 | * @return bool  | 
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| 53 | */  | 
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| 54 | public function hasClass($class)  | 
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| 58 | }  | 
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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.