Complex classes like Promise 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 Promise, and based on these observations, apply Extract Interface, too.
1 | <?php |
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9 | class Promise implements PromiseInterface |
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10 | { |
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11 | use PromiseTrait; |
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12 | |||
13 | /** |
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14 | * @var PromiseInterface|null |
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15 | */ |
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16 | protected $result; |
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17 | |||
18 | /** |
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19 | * @var callable[] |
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20 | */ |
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21 | protected $handlers; |
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22 | |||
23 | /** |
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24 | * @var callable |
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25 | */ |
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26 | protected $canceller; |
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27 | |||
28 | /** |
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29 | * @var int |
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30 | */ |
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31 | protected $currentCancellations; |
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32 | |||
33 | /** |
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34 | * @var int |
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35 | */ |
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36 | protected $requiredCancellations; |
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37 | |||
38 | /** |
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39 | * @param callable|null $resolver |
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40 | * @param callable|null $canceller |
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41 | */ |
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42 | 374 | public function __construct(callable $resolver = null, callable $canceller = null) |
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62 | |||
63 | /** |
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64 | * |
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65 | */ |
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66 | 103 | public function __destruct() |
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74 | |||
75 | /** |
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76 | * @override |
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77 | * @inheritDoc |
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78 | */ |
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79 | 222 | public function then(callable $onFulfilled = null, callable $onRejected = null, callable $onCancel = null) |
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113 | |||
114 | /** |
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115 | * @override |
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116 | * @inheritDoc |
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117 | */ |
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118 | 80 | public function done(callable $onFulfilled = null, callable $onRejected = null, callable $onCancel = null) |
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130 | |||
131 | /** |
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132 | * @override |
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133 | * @inheritDoc |
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134 | */ |
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135 | 18 | public function spread(callable $onFulfilled = null, callable $onRejected = null, callable $onCancel = null) |
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149 | |||
150 | /** |
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151 | * @override |
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152 | * @inheritDoc |
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153 | */ |
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154 | 8 | public function success(callable $onSuccess) |
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158 | |||
159 | /** |
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160 | * @override |
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161 | * @inheritDoc |
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162 | */ |
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163 | 10 | public function failure(callable $onFailure) |
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167 | |||
168 | /** |
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169 | * @override |
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170 | * @inheritDoc |
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171 | */ |
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172 | 8 | public function abort(callable $onCancel) |
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176 | |||
177 | /** |
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178 | * @override |
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179 | * @inheritDoc |
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180 | */ |
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181 | 58 | public function always(callable $onFulfilledOrRejected) |
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201 | |||
202 | /** |
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203 | * @override |
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204 | * @inheritDoc |
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205 | */ |
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206 | 34 | public function isPending() |
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210 | |||
211 | /** |
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212 | * @override |
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213 | * @inheritDoc |
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214 | */ |
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215 | 8 | public function isFulfilled() |
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219 | |||
220 | /** |
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221 | * @override |
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222 | * @inheritDoc |
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223 | */ |
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224 | 8 | public function isRejected() |
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228 | |||
229 | /** |
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230 | * @override |
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231 | * @inheritDoc |
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232 | */ |
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233 | 10 | public function isCancelled() |
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237 | |||
238 | /** |
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239 | * @override |
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240 | * @inheritDoc |
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241 | */ |
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242 | public function getPromise() |
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246 | |||
247 | /** |
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248 | * @override |
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249 | * @inheritDoc |
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250 | */ |
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251 | 144 | public function resolve($value = null) |
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260 | |||
261 | /** |
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262 | * @override |
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263 | * @inheritDoc |
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264 | */ |
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265 | 114 | public function reject($reason = null) |
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274 | |||
275 | /** |
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276 | * @override |
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277 | * @inheritDoc |
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278 | */ |
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279 | 121 | public function cancel($reason = null) |
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302 | |||
303 | /** |
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304 | * Return primitive value associated with Promise. |
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305 | * |
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306 | * @return mixed|null |
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307 | */ |
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308 | protected function getValue() |
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312 | |||
313 | /** |
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314 | * Return rejection or cancellation reason for Promise. |
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315 | * |
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316 | * @return Error|Exception|string|null |
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317 | */ |
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318 | protected function getReason() |
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322 | |||
323 | /** |
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324 | * Settle Promise with another Promise. |
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325 | * |
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326 | * @see PromiseInterface::resolve |
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327 | * @see PromiseInterface::reject |
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328 | * @see PromiseInterface::cancel |
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329 | * |
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330 | * @param PromiseInterface $promise |
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331 | * @return PromiseInterface |
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332 | * @resolves mixed|null |
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333 | * @rejects Error|Exception|string|null |
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334 | * @cancels Error|Exception|string|null |
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335 | */ |
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336 | 330 | protected function settle(PromiseInterface $promise) |
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350 | |||
351 | /** |
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352 | * Get Promise result. Returns fulfilled, rejected or cancelled Promise for settled Promises or null for pending. |
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353 | * |
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354 | * @return PromiseInterface|null |
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355 | */ |
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356 | 168 | protected function getResult() |
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365 | |||
366 | /** |
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367 | * Mutate resolver. |
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368 | * |
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369 | * @param callable|null $resolver |
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370 | */ |
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371 | 374 | protected function mutate(callable $resolver = null) |
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401 | } |
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402 |
If you define a variable conditionally, it can happen that it is not defined for all execution paths.
Let’s take a look at an example:
In the above example, the variable $x is defined if you pass “foo” or “bar” as argument for $a. However, since the switch statement has no default case statement, if you pass any other value, the variable $x would be undefined.
Available Fixes
Check for existence of the variable explicitly:
Define a default value for the variable:
Add a value for the missing path: