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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8 | class Promise implements PromiseInterface |
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9 | { |
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10 | /** |
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11 | * @var integer |
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12 | */ |
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13 | private $state = self::STATE_PENDING; |
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14 | |||
15 | /** |
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16 | * @var mixed |
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17 | */ |
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18 | private $current; |
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19 | |||
20 | /** |
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21 | * @var array |
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22 | */ |
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23 | private $context = []; |
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24 | |||
25 | /** |
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26 | * @var \Closure |
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27 | */ |
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28 | private $waitCallback; |
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29 | |||
30 | /** |
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31 | * @var \Closure |
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32 | */ |
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33 | private $cancelCallback; |
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34 | |||
35 | /** |
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36 | * @var boolean |
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37 | */ |
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38 | private $isStateTransformed; |
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39 | |||
40 | /** |
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41 | * Appends fulfillment and rejection handlers to the promise, and returns an immutable |
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42 | * new promise resolving to the return value of the handler. |
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43 | * |
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44 | * @param \Closure $onFulfilled Callback to be called when promise state is fulfilled. |
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45 | * @param \Closure $onRejected Callback to be called when promise state is rejected. |
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46 | * @return Promise |
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47 | */ |
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48 | public function then($onFulfilled = null, $onRejected = null) |
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49 | { |
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50 | if ($this->state === self::STATE_PENDING) { |
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51 | $q = new Promise(); |
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52 | $this->context[] = [$q, $onFulfilled, $onRejected]; |
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53 | |||
54 | return $q; |
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55 | } |
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56 | |||
57 | if ($this->state === self::STATE_FULFILLED) { |
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58 | return $onFulfilled |
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59 | ? (new FulfilledPromise($this->current))->then($onFulfilled, null) |
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60 | : new FulfilledPromise($this->current); |
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61 | } |
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62 | |||
63 | return $onRejected |
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64 | ? (new RejectedPromise($this->current))->then(null, $onRejected) |
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65 | : new RejectedPromise($this->current); |
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66 | } |
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67 | |||
68 | /** |
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69 | * Set waiting callback. |
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70 | * |
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71 | * @param \Closure $callback Callback to be set. |
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72 | * @return void |
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73 | */ |
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74 | public function setWaitCallback(\Closure $callback = null) |
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75 | { |
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76 | if (!($callback instanceof \Closure)) { |
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77 | throw new \InvalidArgumentException( |
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78 | sprintf("Parameter 1 of %s must be a valid callback.", __METHOD__) |
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79 | ); |
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80 | } |
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81 | |||
82 | $this->waitCallback = $callback; |
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83 | } |
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84 | |||
85 | /** |
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86 | * Set cancellation callback. |
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87 | * |
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88 | * @param \Closure $callback Callback to be set. |
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89 | * @return void |
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90 | */ |
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91 | public function setCancelCallback(\Closure $callback = null) |
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92 | { |
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93 | if (!($callback instanceof \Closure)) { |
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94 | throw new \InvalidArgumentException( |
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95 | sprintf("Parameter 1 of %s must be a valid callback.", __METHOD__) |
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96 | ); |
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97 | } |
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98 | |||
99 | $this->cancelCallback = $callback; |
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100 | } |
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101 | |||
102 | /** |
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103 | * Comparing current promise state to new state and current promise value |
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104 | * to new value. |
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105 | * |
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106 | * @param mixed $value Value to be compare. |
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107 | * @param integer $state New promise state to be compare. |
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108 | * @return null|boolean |
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109 | */ |
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110 | private function validateState($value, $state) |
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111 | { |
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112 | if ($this->state !== self::STATE_PENDING) { |
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113 | if ($value === $this->current && $state === $this->state) { |
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114 | return null; |
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115 | } |
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116 | |||
117 | $prevStatus = $this->state; |
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118 | $currentStatus = $state; |
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119 | |||
120 | throw $this->state === $state |
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121 | ? new \LogicException( |
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122 | sprintf("State of the promise is already %s", $prevStatus == 4 ? 'fulfilled' : 'rejected') |
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123 | ) |
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124 | : new \LogicException( |
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125 | sprintf( |
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126 | "Unable to change %s promise to %s", |
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127 | $prevStatus == 4 ? 'fulfilled' : 'rejected', |
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128 | $currentStatus == 4 ? 'fulfilled' : 'rejected' |
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129 | ) |
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130 | ); |
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131 | } |
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132 | |||
133 | if ($value === $this) { |
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134 | throw new \LogicException( |
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135 | "Unable to fulfill or reject a promise with itself." |
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136 | ); |
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137 | } |
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138 | |||
139 | return true; |
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140 | } |
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141 | |||
142 | /** |
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143 | * {@inheritdoc} |
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144 | */ |
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145 | public function resolve($value) |
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146 | { |
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147 | $this->isStateTransformed = $this->validateState($value, self::STATE_FULFILLED); |
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148 | |||
149 | if ($this->isStateTransformed) { |
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150 | $this->setState(self::STATE_FULFILLED); |
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151 | $this->trigger($value); |
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152 | } |
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153 | } |
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154 | |||
155 | /** |
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156 | * {@inheritdoc} |
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157 | */ |
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158 | public function reject($reason) |
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159 | { |
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160 | $this->isStateTransformed = $this->validateState($reason, self::STATE_REJECTED); |
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161 | |||
162 | if ($this->isStateTransformed) { |
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163 | $this->setState(self::STATE_REJECTED); |
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164 | $this->trigger($reason); |
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165 | } |
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166 | } |
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167 | |||
168 | /** |
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169 | * Synchronously forces promise to complete using wait method. |
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170 | * |
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171 | * @return mixed |
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172 | */ |
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173 | public function wait() |
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174 | { |
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175 | $this->waitInPendingState(); |
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176 | |||
177 | $q = $this->current instanceof PromiseInterface |
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178 | ? $this->current->wait() |
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179 | : $this->current; |
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180 | |||
181 | if ($this->current instanceof PromiseInterface || $this->currentState() === self::STATE_FULFILLED) { |
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182 | return $q; |
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183 | } else { |
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184 | throw $q instanceof \Exception |
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185 | ? $q |
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186 | : new \Exception($q); |
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187 | } |
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188 | } |
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189 | |||
190 | /** |
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191 | * Cancel a promise that has not yet been fulfilled. |
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192 | * |
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193 | * @return mixed |
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194 | */ |
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195 | public function cancel() |
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196 | { |
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197 | if ($this->currentState() !== self::STATE_PENDING) { |
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198 | return; |
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199 | } |
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200 | |||
201 | if ($this->cancelCallback) { |
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202 | $cancelCallback = $this->cancelCallback; |
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203 | $this->cancelCallback = null; |
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204 | |||
205 | try { |
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206 | $cancelCallback(); |
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207 | } catch (\Exception $e) { |
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208 | $this->reject($e); |
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209 | } |
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210 | } |
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211 | |||
212 | if ($this->currentState() === self::STATE_PENDING) { |
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213 | $this->reject('Promise has been cancelled.'); |
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214 | } |
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215 | |||
216 | $e = $this->current instanceof PromiseInterface |
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217 | ? $this->current->cancel() |
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218 | : $this->current; |
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219 | |||
220 | if ($this->current instanceof PromiseInterface || $this->currentState() === self::STATE_REJECTED) { |
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221 | return $e; |
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222 | } |
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223 | } |
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224 | |||
225 | /** |
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226 | * {@inheritdoc} |
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227 | */ |
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228 | public function currentState() |
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232 | |||
233 | /** |
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234 | * Invoking promise handler based on current state and given value. |
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235 | * |
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236 | * @param mixed $value |
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237 | * @return void |
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238 | */ |
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239 | private function trigger($value) |
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240 | { |
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275 | |||
276 | /** |
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277 | * Invoking handler based on given context, index, and value. |
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278 | * |
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279 | * @param array $context |
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280 | * @param integer $index |
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281 | * @param mixed $value |
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282 | * @return void |
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283 | */ |
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284 | private static function invokeContext($context, $index, $value) |
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306 | |||
307 | /** |
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308 | * Set promise state to given state. |
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309 | * |
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310 | * @param integer $state |
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311 | * @return void |
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312 | */ |
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313 | private function setState($state) |
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325 | |||
326 | /** |
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327 | * Synchronously forces promise to wait when current promise state is pending. |
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328 | * |
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329 | * @return void |
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330 | */ |
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331 | private function waitInPendingState() |
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357 | } |
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358 |