Complex classes like Analyzer 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 Analyzer, and based on these observations, apply Extract Interface, too.
| 1 | <?php |
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| 25 | class Analyzer |
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| 26 | { |
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| 27 | /** |
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| 28 | * @var array|RuleDelegate[] |
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| 29 | */ |
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| 30 | protected $rules = []; |
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| 31 | |||
| 32 | /** |
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| 33 | * Parsed rules. |
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| 34 | * @var array|AbstractBuilder[] |
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| 35 | */ |
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| 36 | protected $parsedRules; |
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| 37 | |||
| 38 | /** |
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| 39 | * Counter to auto-name transitional rules. |
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| 40 | * @var int |
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| 41 | */ |
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| 42 | protected $transitionalRuleCounter = 0; |
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| 43 | |||
| 44 | /** |
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| 45 | * Rule name being analyzed. |
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| 46 | * @var string |
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| 47 | */ |
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| 48 | private $ruleName; |
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| 49 | |||
| 50 | /** |
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| 51 | * @param RuleDelegate $delegate |
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| 52 | */ |
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| 53 | public function addRuleDelegate(RuleDelegate $delegate): void |
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| 57 | |||
| 58 | /** |
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| 59 | * Build the analyzer of the rules (does not analyze the rules). |
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| 60 | * |
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| 61 | * @return Rule[]|\Traversable |
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| 62 | * @throws GrammarException |
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| 63 | */ |
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| 64 | public function analyze(): iterable |
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| 99 | |||
| 100 | /** |
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| 101 | * Implementation of “rule”. |
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| 102 | * |
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| 103 | * @param LookaheadIterator $tokens |
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| 104 | * @param string|null $pNodeId |
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| 105 | * @return string|int|null |
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| 106 | * @throws GrammarException |
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| 107 | */ |
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| 108 | protected function rule(LookaheadIterator $tokens, &$pNodeId) |
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| 112 | |||
| 113 | /** |
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| 114 | * Implementation of “choice”. |
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| 115 | * |
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| 116 | * @param LookaheadIterator $tokens |
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| 117 | * @param string|null $pNodeId |
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| 118 | * @return string|int|null |
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| 119 | * @throws GrammarException |
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| 120 | */ |
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| 121 | protected function choice(LookaheadIterator $tokens, &$pNodeId) |
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| 170 | |||
| 171 | /** |
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| 172 | * Implementation of “concatenation”. |
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| 173 | * |
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| 174 | * @param LookaheadIterator $tokens |
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| 175 | * @param string|null $pNodeId |
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| 176 | * @return string|int|null |
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| 177 | * @throws GrammarException |
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| 178 | */ |
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| 179 | protected function concatenation(LookaheadIterator $tokens, &$pNodeId) |
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| 209 | |||
| 210 | /** |
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| 211 | * Implementation of “repetition”. |
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| 212 | * |
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| 213 | * @param LookaheadIterator $tokens |
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| 214 | * @param string|null $pNodeId |
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| 215 | * @return string|int|null |
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| 216 | * @throws GrammarException |
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| 217 | */ |
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| 218 | protected function repetition(LookaheadIterator $tokens, &$pNodeId) |
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| 291 | |||
| 292 | /** |
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| 293 | * Implementation of “simple”. |
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| 294 | * |
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| 295 | * @param LookaheadIterator $tokens |
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| 296 | * @param int|string|null $pNodeId |
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| 297 | * @return string|int|null |
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| 298 | * @throws GrammarException |
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| 299 | */ |
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| 300 | protected function simple(LookaheadIterator $tokens, &$pNodeId) |
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| 319 | |||
| 320 | /** |
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| 321 | * @param LookaheadIterator $tokens |
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| 322 | * @param int|string|null $pNodeId |
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| 323 | * @return int|null|string |
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| 324 | * @throws GrammarException |
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| 325 | */ |
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| 326 | protected function group(LookaheadIterator $tokens, &$pNodeId) |
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| 343 | |||
| 344 | /** |
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| 345 | * @param LookaheadIterator $tokens |
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| 346 | * @param bool $kept |
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| 347 | * @return int|string|null |
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| 348 | */ |
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| 349 | protected function token(LookaheadIterator $tokens, bool $kept = true) |
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| 360 | |||
| 361 | /** |
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| 362 | * @param LookaheadIterator $tokens |
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| 363 | * @return int|string |
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| 364 | * @throws GrammarException |
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| 365 | */ |
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| 366 | protected function invoke(LookaheadIterator $tokens) |
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| 390 | } |
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| 391 |
This error can happen if you refactor code and forget to move the variable initialization.
Let’s take a look at a simple example:
The above code is perfectly fine. Now imagine that we re-order the statements:
In that case,
$xwould be read before it is initialized. This was a very basic example, however the principle is the same for the found issue.