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 Map 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 Map, and based on these observations, apply Extract Interface, too.
1 | <?php |
||
14 | final class Map implements \IteratorAggregate, \ArrayAccess, Collection |
||
15 | { |
||
16 | use Traits\Collection; |
||
17 | use Traits\SquaredCapacity; |
||
18 | |||
19 | const MIN_CAPACITY = 8; |
||
20 | |||
21 | /** |
||
22 | * @var Pair[] |
||
23 | */ |
||
24 | private $pairs; |
||
25 | |||
26 | /** |
||
27 | * Creates an instance using the values of an array or Traversable object. |
||
28 | * |
||
29 | * Should an integer be provided the Map will allocate the memory capacity |
||
30 | * to the size of $values. |
||
31 | * |
||
32 | * @param array|\Traversable|int|null $values |
||
33 | */ |
||
34 | public function __construct($values = null) |
||
43 | |||
44 | /** |
||
45 | * @inheritDoc |
||
46 | */ |
||
47 | public function clear() |
||
52 | |||
53 | /** |
||
54 | * Removes all Pairs from the Map |
||
55 | * |
||
56 | * @param mixed[] $keys |
||
57 | */ |
||
58 | public function removeAll($keys) |
||
64 | |||
65 | /** |
||
66 | * Return the first Pair from the Map |
||
67 | * |
||
68 | * @return Pair |
||
69 | * |
||
70 | * @throws UnderflowException |
||
71 | */ |
||
72 | public function first(): Pair |
||
80 | |||
81 | /** |
||
82 | * Return the last Pair from the Map |
||
83 | * |
||
84 | * @return Pair |
||
85 | * |
||
86 | * @throws UnderflowException |
||
87 | */ |
||
88 | public function last(): Pair |
||
96 | |||
97 | /** |
||
98 | * Return the pair at a specified position in the Map |
||
99 | * |
||
100 | * @param int $position |
||
101 | * |
||
102 | * @return Pair |
||
103 | * |
||
104 | * @throws OutOfRangeException |
||
105 | */ |
||
106 | public function skip(int $position): Pair |
||
114 | |||
115 | /** |
||
116 | * Merge an array of values with the current Map |
||
117 | * |
||
118 | * @param array|\Traversable $values |
||
119 | * |
||
120 | * @return Map |
||
121 | */ |
||
122 | public function merge($values): Map |
||
129 | |||
130 | /** |
||
131 | * Intersect |
||
132 | * |
||
133 | * @param Map $map |
||
134 | * |
||
135 | * @return Map |
||
136 | */ |
||
137 | public function intersect(Map $map): Map |
||
143 | |||
144 | /** |
||
145 | * Diff |
||
146 | * |
||
147 | * @param Map $map |
||
148 | * |
||
149 | * @return Map |
||
150 | */ |
||
151 | public function diff(Map $map): Map |
||
157 | |||
158 | /** |
||
159 | * XOR |
||
160 | * |
||
161 | * @param Map $map |
||
162 | * |
||
163 | * @return Map |
||
164 | */ |
||
165 | public function xor(Map $map): Map |
||
171 | |||
172 | /** |
||
173 | * Identical |
||
174 | * |
||
175 | * @param mixed $a |
||
176 | * @param mixed $b |
||
177 | * |
||
178 | * @return bool |
||
179 | */ |
||
180 | private function keysAreEqual($a, $b): bool |
||
188 | |||
189 | /** |
||
190 | * @param $key |
||
191 | * |
||
192 | * @return Pair|null |
||
193 | */ |
||
194 | private function lookupKey($key) |
||
202 | |||
203 | /** |
||
204 | * @param $value |
||
205 | * |
||
206 | * @return Pair|null |
||
207 | */ |
||
208 | private function lookupValue($value) |
||
216 | |||
217 | /** |
||
218 | * |
||
219 | */ |
||
220 | View Code Duplication | private function contains(string $lookup, array $values): bool |
|
234 | |||
235 | /** |
||
236 | * Returns whether an association for all of zero or more keys exist. |
||
237 | * |
||
238 | * @param mixed ...$keys |
||
239 | * |
||
240 | * @return bool true if at least one value was provided and the map |
||
241 | * contains all given keys, false otherwise. |
||
242 | */ |
||
243 | public function hasKey(...$keys): bool |
||
247 | |||
248 | /** |
||
249 | * Returns whether an association for all of zero or more values exist. |
||
250 | * |
||
251 | * @param mixed ...$values |
||
252 | * |
||
253 | * @return bool true if at least one value was provided and the map |
||
254 | * contains all given values, false otherwise. |
||
255 | */ |
||
256 | public function hasValue(...$values): bool |
||
260 | |||
261 | /** |
||
262 | * @inheritDoc |
||
263 | */ |
||
264 | public function count(): int |
||
268 | |||
269 | /** |
||
270 | * Returns a new map containing only the values for which a predicate |
||
271 | * returns true. A boolean test will be used if a predicate is not provided. |
||
272 | * |
||
273 | * @param callable|null $predicate Accepts a key and a value, and returns: |
||
274 | * true : include the value, |
||
275 | * false: skip the value. |
||
276 | * |
||
277 | * @return Map |
||
278 | */ |
||
279 | View Code Duplication | public function filter(callable $predicate = null): Map |
|
291 | |||
292 | /** |
||
293 | * Returns the value associated with a key, or an optional default if the |
||
294 | * key is not associated with a value. |
||
295 | * |
||
296 | * @param mixed $key |
||
297 | * @param mixed $default |
||
298 | * |
||
299 | * @return mixed The associated value or fallback default if provided. |
||
300 | * |
||
301 | * @throws OutOfBoundsException if no default was provided and the key is |
||
302 | * not associated with a value. |
||
303 | */ |
||
304 | public function get($key, $default = null) |
||
316 | |||
317 | /** |
||
318 | * Returns a set of all the keys in the map. |
||
319 | * |
||
320 | * @return Set |
||
321 | */ |
||
322 | public function keys(): Set |
||
332 | |||
333 | /** |
||
334 | * Returns a new map using the results of applying a callback to each value. |
||
335 | * The keys will be keysAreEqual in both maps. |
||
336 | * |
||
337 | * @param callable $callback Accepts two arguments: key and value, should |
||
338 | * return what the updated value will be. |
||
339 | * |
||
340 | * @return Map |
||
341 | */ |
||
342 | public function map(callable $callback): Map |
||
352 | |||
353 | /** |
||
354 | * Returns a sequence of pairs representing all associations. |
||
355 | * |
||
356 | * @return Sequence |
||
357 | */ |
||
358 | public function pairs(): Sequence |
||
368 | |||
369 | /** |
||
370 | * Associates a key with a value, replacing a previous association if there |
||
371 | * was one. |
||
372 | * |
||
373 | * @param mixed $key |
||
374 | * @param mixed $value |
||
375 | */ |
||
376 | public function put($key, $value) |
||
388 | |||
389 | /** |
||
390 | * Creates associations for all keys and corresponding values of either an |
||
391 | * array or iterable object. |
||
392 | * |
||
393 | * @param array|\Traversable $values |
||
394 | */ |
||
395 | public function putAll($values) |
||
401 | |||
402 | /** |
||
403 | * Iteratively reduces the map to a single value using a callback. |
||
404 | * |
||
405 | * @param callable $callback Accepts the carry, key, and value, and |
||
406 | * returns an updated carry value. |
||
407 | * |
||
408 | * @param mixed|null $initial Optional initial carry value. |
||
409 | * |
||
410 | * @return mixed The carry value of the final iteration, or the initial |
||
411 | * value if the map was empty. |
||
412 | */ |
||
413 | public function reduce(callable $callback, $initial = null) |
||
423 | |||
424 | private function delete(int $position) |
||
434 | |||
435 | /** |
||
436 | * Removes a key's association from the map and returns the associated value |
||
437 | * or a provided default if provided. |
||
438 | * |
||
439 | * @param mixed $key |
||
440 | * @param mixed $default |
||
441 | * |
||
442 | * @return mixed The associated value or fallback default if provided. |
||
443 | * |
||
444 | * @throws \OutOfBoundsException if no default was provided and the key is |
||
445 | * not associated with a value. |
||
446 | */ |
||
447 | public function remove($key, $default = null) |
||
462 | |||
463 | /** |
||
464 | * Returns a reversed copy of the map. |
||
465 | */ |
||
466 | public function reverse(): Map |
||
473 | |||
474 | /** |
||
475 | * Returns a sub-sequence of a given length starting at a specified offset. |
||
476 | * |
||
477 | * @param int $offset If the offset is non-negative, the map will |
||
478 | * start at that offset in the map. If offset is |
||
479 | * negative, the map will start that far from the |
||
480 | * end. |
||
481 | * |
||
482 | * @param int|null $length If a length is given and is positive, the |
||
483 | * resulting set will have up to that many pairs in |
||
484 | * it. If the requested length results in an |
||
485 | * overflow, only pairs up to the end of the map |
||
486 | * will be included. |
||
487 | * |
||
488 | * If a length is given and is negative, the map |
||
489 | * will stop that many pairs from the end. |
||
490 | * |
||
491 | * If a length is not provided, the resulting map |
||
492 | * will contains all pairs between the offset and |
||
493 | * the end of the map. |
||
494 | * |
||
495 | * @return Map |
||
496 | */ |
||
497 | public function slice(int $offset, int $length = null): Map |
||
513 | |||
514 | /** |
||
515 | * Returns a sorted copy of the map, based on an optional callable |
||
516 | * comparator. The map will be sorted by value. |
||
517 | * |
||
518 | * @param callable|null $comparator Accepts two values to be compared. |
||
519 | * |
||
520 | * @return Map |
||
521 | */ |
||
522 | View Code Duplication | public function sort(callable $comparator = null): Map |
|
539 | |||
540 | /** |
||
541 | * Returns a sorted copy of the map, based on an optional callable |
||
542 | * comparator. The map will be sorted by key. |
||
543 | * |
||
544 | * @param callable|null $comparator Accepts two keys to be compared. |
||
545 | * |
||
546 | * @return Map |
||
547 | */ |
||
548 | View Code Duplication | public function ksort(callable $comparator = null): Map |
|
565 | |||
566 | /** |
||
567 | * @inheritDoc |
||
568 | */ |
||
569 | public function toArray(): array |
||
579 | |||
580 | /** |
||
581 | * Returns a sequence of all the associated values in the Map. |
||
582 | * |
||
583 | * @return Sequence |
||
584 | */ |
||
585 | public function values(): Sequence |
||
595 | |||
596 | /** |
||
597 | * Get iterator |
||
598 | */ |
||
599 | public function getIterator() |
||
605 | |||
606 | /** |
||
607 | * Debug Info |
||
608 | */ |
||
609 | public function __debugInfo() |
||
613 | |||
614 | /** |
||
615 | * @inheritdoc |
||
616 | */ |
||
617 | public function offsetSet($offset, $value) |
||
621 | |||
622 | /** |
||
623 | * @inheritdoc |
||
624 | * |
||
625 | * @throws OutOfBoundsException |
||
626 | */ |
||
627 | public function &offsetGet($offset) |
||
637 | |||
638 | /** |
||
639 | * @inheritdoc |
||
640 | */ |
||
641 | public function offsetUnset($offset) |
||
645 | |||
646 | /** |
||
647 | * @inheritdoc |
||
648 | */ |
||
649 | public function offsetExists($offset) |
||
653 | } |
||
654 |
This check looks for multiple assignments in successive lines of code. It will report an issue if the operators are not in a straight line.
To visualize
will produce issues in the first and second line, while this second example
will produce no issues.