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 QueryBuilder 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 QueryBuilder, and based on these observations, apply Extract Interface, too.
1 | <?php |
||
17 | class QueryBuilder implements QueryInterface |
||
18 | { |
||
19 | /* @var string The modifier. SELECT, INSERT INTO, UPDATE or DELETE */ |
||
20 | private $modifier; |
||
21 | |||
22 | /* @var string The table name. */ |
||
23 | private $table; |
||
24 | |||
25 | /* @var array The columns. */ |
||
26 | private $columns; |
||
27 | |||
28 | /* @var array The values. */ |
||
29 | private $values; |
||
30 | |||
31 | /* @var array The join conditions. */ |
||
32 | private $join; |
||
33 | |||
34 | /* @var QueryExpression The where clause. */ |
||
35 | private $where; |
||
36 | |||
37 | /* @var array The group by conditions. */ |
||
38 | private $groupBy; |
||
39 | |||
40 | /* @var array The order by conditions. */ |
||
41 | private $orderBy; |
||
42 | |||
43 | /* @var string The limit. */ |
||
44 | private $limit; |
||
45 | |||
46 | /* @var string The offset. */ |
||
47 | private $offset; |
||
48 | |||
49 | /** |
||
50 | * Construct a query builder object with the given table. |
||
51 | * |
||
52 | * @param string $table |
||
53 | */ |
||
54 | 45 | public function __construct($table) |
|
62 | |||
63 | /** |
||
64 | * Returns a string representation of the query object. |
||
65 | * |
||
66 | * @return string a string representation of the query object. |
||
67 | */ |
||
68 | 45 | public function __toString() |
|
87 | |||
88 | /** |
||
89 | * {@inheritdoc} |
||
90 | */ |
||
91 | 33 | public function select($columns = ['*']) |
|
98 | |||
99 | /** |
||
100 | * Returns the select clause. |
||
101 | * |
||
102 | * @return string the select clause. |
||
103 | */ |
||
104 | 33 | private function getSelectClause() |
|
108 | |||
109 | /** |
||
110 | * Returns the select query. |
||
111 | * |
||
112 | * @return string the select query. |
||
113 | */ |
||
114 | 33 | private function getSelectQuery() |
|
144 | |||
145 | /** |
||
146 | * {@inheritdoc} |
||
147 | */ |
||
148 | 3 | public function insert(array $values) |
|
155 | |||
156 | /** |
||
157 | * Returns the insert clause. |
||
158 | * |
||
159 | * @return string the insert clause. |
||
160 | */ |
||
161 | 3 | private function getInsertClause() |
|
173 | |||
174 | /** |
||
175 | * Returns the insert query. |
||
176 | * |
||
177 | * @return string the insert query. |
||
178 | */ |
||
179 | 3 | private function getInsertQuery() |
|
183 | |||
184 | /** |
||
185 | * {@inheritdoc} |
||
186 | */ |
||
187 | 4 | public function update(array $values) |
|
194 | |||
195 | /** |
||
196 | * Returns the update clause. |
||
197 | * |
||
198 | * @return string the update clause. |
||
199 | */ |
||
200 | 4 | private function getUpdateClause() |
|
210 | |||
211 | /** |
||
212 | * Returns the update query. |
||
213 | * |
||
214 | * @return string the update query. |
||
215 | */ |
||
216 | 4 | View Code Duplication | private function getUpdateQuery() |
230 | |||
231 | /** |
||
232 | * {@inheritdoc} |
||
233 | */ |
||
234 | 3 | public function delete() |
|
240 | |||
241 | /** |
||
242 | * Returns the delete clause. |
||
243 | * |
||
244 | * @return string the delete clause. |
||
245 | */ |
||
246 | 3 | private function getDeleteClause() |
|
250 | |||
251 | /** |
||
252 | * Returns the delete query. |
||
253 | * |
||
254 | * @return string the delete query. |
||
255 | */ |
||
256 | 3 | View Code Duplication | private function getDeleteQuery() |
271 | |||
272 | /** |
||
273 | * {@inheritdoc} |
||
274 | */ |
||
275 | 2 | public function join($table, $primary, $operator, $secondary) |
|
281 | |||
282 | /** |
||
283 | * {@inheritdoc} |
||
284 | */ |
||
285 | 2 | public function leftJoin($table, $primary, $operator, $secondary) |
|
291 | |||
292 | /** |
||
293 | * {@inheritdoc} |
||
294 | */ |
||
295 | 2 | public function rightJoin($table, $primary, $operator, $secondary) |
|
301 | |||
302 | /** |
||
303 | * {@inheritdoc} |
||
304 | */ |
||
305 | 2 | public function crossJoin($table, $primary, $operator, $secondary) |
|
311 | |||
312 | 33 | private function getJoinClause() |
|
322 | |||
323 | /** |
||
324 | * {@inheritdoc} |
||
325 | */ |
||
326 | 15 | public function where(QueryExpression $whereClause) |
|
332 | |||
333 | /** |
||
334 | * Returns the where clause. |
||
335 | * |
||
336 | * @return string the where clause. |
||
337 | */ |
||
338 | 40 | private function getWhereClause() |
|
346 | |||
347 | /** |
||
348 | * {@inheritdoc} |
||
349 | */ |
||
350 | 2 | public function groupBy($column) |
|
356 | |||
357 | /** |
||
358 | * Returns the group by clause. |
||
359 | * |
||
360 | * @return string the group by clause. |
||
361 | */ |
||
362 | 33 | private function getGroupByClause() |
|
370 | |||
371 | /** |
||
372 | * {@inheritdoc} |
||
373 | */ |
||
374 | 4 | public function orderBy($column, $order = null) |
|
386 | |||
387 | /** |
||
388 | * Returns the order by clause. |
||
389 | * |
||
390 | * @return string the order by clause. |
||
391 | */ |
||
392 | 33 | private function getOrderByClause() |
|
400 | |||
401 | /** |
||
402 | * {@inheritdoc} |
||
403 | */ |
||
404 | 6 | public function limit($limit) |
|
410 | |||
411 | /** |
||
412 | * Returns the limit clause. |
||
413 | * |
||
414 | * @return string the limit clause. |
||
415 | */ |
||
416 | 40 | private function getLimitClause() |
|
424 | |||
425 | /** |
||
426 | * {@inheritdoc} |
||
427 | */ |
||
428 | 2 | public function offset($offset) |
|
434 | |||
435 | /** |
||
436 | * Returns the offset clause. |
||
437 | * |
||
438 | * @return string the offset clause. |
||
439 | */ |
||
440 | 33 | private function getOffsetClause() |
|
448 | } |
||
449 |
Our type inference engine has found an assignment to a property that is incompatible with the declared type of that property.
Either this assignment is in error or the assigned type should be added to the documentation/type hint for that property..