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 |
||
12 | class Comment_Meta_Container extends Container { |
||
13 | protected $comment_id; |
||
14 | |||
15 | /** |
||
16 | * Create a new container |
||
17 | * |
||
18 | * @param string $unique_id Unique id of the container |
||
19 | * @param string $title title of the container |
||
20 | * @param string $type Type of the container |
||
21 | **/ |
||
22 | View Code Duplication | public function __construct( $unique_id, $title, $type ) { |
|
29 | |||
30 | /** |
||
31 | * Perform instance initialization |
||
32 | **/ |
||
33 | public function init() { |
||
41 | |||
42 | /** |
||
43 | * Checks whether the current request is valid |
||
44 | * |
||
45 | * @return bool |
||
46 | **/ |
||
47 | public function is_valid_save() { |
||
50 | |||
51 | /** |
||
52 | * Perform save operation after successful is_valid_save() check. |
||
53 | * The call is propagated to all fields in the container. |
||
54 | * |
||
55 | * @param int $comment_id ID of the comment against which save() is ran |
||
56 | **/ |
||
57 | public function save( $comment_id ) { |
||
69 | |||
70 | /** |
||
71 | * Check container attachment rules against current page request (in admin) |
||
72 | * |
||
73 | * @return bool |
||
74 | **/ |
||
75 | public function is_valid_attach_for_request() { |
||
80 | |||
81 | /** |
||
82 | * Check container attachment rules against object id |
||
83 | * |
||
84 | * @return bool |
||
85 | **/ |
||
86 | public function is_valid_attach_for_object( $object_id = null ) { |
||
89 | |||
90 | /** |
||
91 | * Add meta box to the comment |
||
92 | **/ |
||
93 | public function attach() { |
||
103 | |||
104 | /** |
||
105 | * Output the container markup |
||
106 | **/ |
||
107 | public function render() { |
||
110 | |||
111 | /** |
||
112 | * Set the comment ID the container will operate with. |
||
113 | * |
||
114 | * @param int $comment_id |
||
115 | **/ |
||
116 | public function set_comment_id( $comment_id ) { |
||
120 | } |
||
121 |
Let’s take a look at an example:
In the above example, the authenticate() method works fine as long as you just pass instances of MyUser. However, if you now also want to pass a different implementation of User which does not have a getDisplayName() method, the code will break.
Available Fixes
Change the type-hint for the parameter:
Add an additional type-check:
Add the method to the interface: