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 DoctrineCollectionDataSource 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 DoctrineCollectionDataSource, and based on these observations, apply Extract Interface, too.
| 1 | <?php | ||
| 16 | final class DoctrineCollectionDataSource extends FilterableDataSource implements IDataSource | ||
| 17 | { | ||
| 18 | |||
| 19 | /** | ||
| 20 | * @var Collection | ||
| 21 | */ | ||
| 22 | private $data_source; | ||
| 23 | |||
| 24 | /** | ||
| 25 | * @var string | ||
| 26 | */ | ||
| 27 | private $primary_key; | ||
| 28 | |||
| 29 | /** | ||
| 30 | * @var Criteria | ||
| 31 | */ | ||
| 32 | private $criteria; | ||
| 33 | |||
| 34 | /** | ||
| 35 | * @var array | ||
| 36 | */ | ||
| 37 | protected $aggregations = []; | ||
| 38 | |||
| 39 | /** | ||
| 40 | * @param Collection $collection | ||
| 41 | * @param string $primary_key | ||
| 42 | */ | ||
| 43 | public function __construct(Collection $collection, $primary_key) | ||
| 49 | |||
| 50 | |||
| 51 | /** | ||
| 52 | * @return Collection | ||
| 53 | */ | ||
| 54 | private function getFilteredCollection() | ||
| 58 | |||
| 59 | |||
| 60 | /******************************************************************************** | ||
| 61 | * IDataSource implementation * | ||
| 62 | ********************************************************************************/ | ||
| 63 | |||
| 64 | |||
| 65 | /** | ||
| 66 | * Get count of data | ||
| 67 | * @return int | ||
| 68 | */ | ||
| 69 | public function getCount() | ||
| 73 | |||
| 74 | |||
| 75 | /** | ||
| 76 | * Get the data | ||
| 77 | * @return array | ||
| 78 | */ | ||
| 79 | public function getData() | ||
| 83 | |||
| 84 | |||
| 85 | /** | ||
| 86 | * Filter data - get one row | ||
| 87 | * @param array $condition | ||
| 88 | * @return static | ||
| 89 | */ | ||
| 90 | public function filterOne(array $condition) | ||
| 99 | |||
| 100 | |||
| 101 | /** | ||
| 102 | * Filter by date | ||
| 103 | * @param Filter\FilterDate $filter | ||
| 104 | * @return void | ||
| 105 | */ | ||
| 106 | public function applyFilterDate(Filter\FilterDate $filter) | ||
| 118 | |||
| 119 | |||
| 120 | /** | ||
| 121 | * Filter by date range | ||
| 122 | * @param Filter\FilterDateRange $filter | ||
| 123 | * @return void | ||
| 124 | */ | ||
| 125 | public function applyFilterDateRange(Filter\FilterDateRange $filter) | ||
| 147 | |||
| 148 | |||
| 149 | /** | ||
| 150 | * Filter by range | ||
| 151 | * @param Filter\FilterRange $filter | ||
| 152 | * @return void | ||
| 153 | */ | ||
| 154 | public function applyFilterRange(Filter\FilterRange $filter) | ||
| 168 | |||
| 169 | |||
| 170 | /** | ||
| 171 | * Filter by keyword | ||
| 172 | * @param Filter\FilterText $filter | ||
| 173 | * @return void | ||
| 174 | */ | ||
| 175 | public function applyFilterText(Filter\FilterText $filter) | ||
| 199 | |||
| 200 | |||
| 201 | /** | ||
| 202 | * Filter by multi select value | ||
| 203 | * @param Filter\FilterMultiSelect $filter | ||
| 204 | * @return void | ||
| 205 | */ | ||
| 206 | public function applyFilterMultiSelect(Filter\FilterMultiSelect $filter) | ||
| 213 | |||
| 214 | |||
| 215 | /** | ||
| 216 | * Filter by select value | ||
| 217 | * @param Filter\FilterSelect $filter | ||
| 218 | * @return void | ||
| 219 | */ | ||
| 220 | public function applyFilterSelect(Filter\FilterSelect $filter) | ||
| 227 | |||
| 228 | |||
| 229 | /** | ||
| 230 | * Apply limit and offset on data | ||
| 231 | * @param int $offset | ||
| 232 | * @param int $limit | ||
| 233 | * @return static | ||
| 234 | */ | ||
| 235 | public function limit($offset, $limit) | ||
| 241 | |||
| 242 | |||
| 243 | /** | ||
| 244 | * Sort data | ||
| 245 | * @param Sorting $sorting | ||
| 246 | * @return static | ||
| 247 | */ | ||
| 248 | public function sort(Sorting $sorting) | ||
| 269 | |||
| 270 | /** | ||
| 271 | * @param string $aggregation_type | ||
| 272 | * @param string $column | ||
| 273 | * @return mixed | ||
| 274 | */ | ||
| 275 | public function addAggregationColumn($aggregation_type, $column) | ||
| 279 | |||
| 280 | /** | ||
| 281 | * get aggregation row | ||
| 282 | * @return array | ||
| 283 | */ | ||
| 284 | View Code Duplication | public function getAggregationData() | |
| 318 | } | ||
| 319 | 
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: