hiqdev /
php-units
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:
| 1 | <?php |
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| 18 | abstract class AbstractQuantity implements QuantityInterface, \JsonSerializable |
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| 19 | { |
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| 20 | /** |
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| 21 | * @var UnitInterface |
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| 22 | */ |
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| 23 | private $unit; |
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| 24 | |||
| 25 | /** |
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| 26 | * @var float|int|string |
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| 27 | */ |
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| 28 | private $quantity; |
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| 29 | |||
| 30 | /** |
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| 31 | * @var UnitInterface |
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| 32 | * @var float|int|string $quantity |
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| 33 | */ |
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| 34 | 10 | private function __construct(UnitInterface $unit, $quantity) |
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| 39 | |||
| 40 | /** |
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| 41 | * Creates quantity with same unit. |
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| 42 | * Optimized to return this if same quantity. |
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| 43 | * @var float|int|string |
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| 44 | */ |
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| 45 | 5 | final protected function repeat($quantity) |
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| 46 | { |
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| 47 | 5 | return $this->quantity === $quantity ? $this : static::create($this->unit, $quantity); |
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| 48 | } |
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| 49 | |||
| 50 | /** |
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| 51 | * {@inheritdoc} |
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| 52 | */ |
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| 53 | 4 | private function getCalculator() |
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| 57 | |||
| 58 | /** |
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| 59 | * {@inheritdoc} |
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| 60 | */ |
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| 61 | 6 | final public function getQuantity() |
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| 65 | |||
| 66 | /** |
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| 67 | * {@inheritdoc} |
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| 68 | */ |
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| 69 | 1 | final public function getUnit() |
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| 73 | |||
| 74 | /** |
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| 75 | * {@inheritdoc} |
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| 76 | */ |
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| 77 | 2 | final public function compare(QuantityInterface $other) |
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| 78 | { |
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| 79 | 2 | $arg = $other->convert($this->unit)->getQuantity(); |
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| 80 | |||
| 81 | 2 | return $this->getCalculator()->compare($this->quantity, $arg); |
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| 82 | } |
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| 83 | |||
| 84 | /** |
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| 85 | * {@inheritdoc} |
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| 86 | */ |
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| 87 | 1 | final public function equals(QuantityInterface $other) |
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| 91 | |||
| 92 | /** |
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| 93 | * {@inheritdoc} |
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| 94 | */ |
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| 95 | 1 | final public function isPositive() |
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| 99 | |||
| 100 | /** |
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| 101 | * {@inheritdoc} |
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| 102 | */ |
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| 103 | 1 | final public function isNegative() |
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| 107 | |||
| 108 | /** |
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| 109 | * {@inheritdoc} |
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| 110 | */ |
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| 111 | 1 | final public function isConvertible(UnitInterface $unit) |
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| 115 | |||
| 116 | /** |
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| 117 | * {@inheritdoc} |
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| 118 | */ |
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| 119 | 5 | final public function convert(UnitInterface $unit) |
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| 125 | |||
| 126 | /** |
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| 127 | * {@inheritdoc} |
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| 128 | */ |
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| 129 | 1 | View Code Duplication | final public function add(QuantityInterface $addend) |
| 130 | { |
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| 131 | 1 | $arg = $addend->convert($this->unit)->getQuantity(); |
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| 132 | 1 | $res = $this->getCalculator()->add($this->quantity, $arg); |
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| 133 | |||
| 134 | 1 | return $this->repeat($res); |
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| 135 | } |
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| 136 | |||
| 137 | /** |
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| 138 | * {@inheritdoc} |
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| 139 | */ |
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| 140 | 1 | View Code Duplication | final public function subtract(QuantityInterface $subtrahend) |
| 141 | { |
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| 142 | 1 | $arg = $subtrahend->convert($this->unit)->getQuantity(); |
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| 143 | 1 | $res = $this->getCalculator()->subtract($this->quantity, $arg); |
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| 144 | |||
| 145 | 1 | return $this->repeat($res); |
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| 146 | } |
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| 147 | |||
| 148 | /** |
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| 149 | * {@inheritdoc} |
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| 150 | */ |
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| 151 | final public function multiply($multiplier) |
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| 157 | |||
| 158 | /** |
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| 159 | * {@inheritdoc} |
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| 160 | */ |
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| 161 | final public function divide($divisor) |
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| 167 | |||
| 168 | /** |
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| 169 | * {@inheritdoc} |
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| 170 | */ |
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| 171 | final public function ceil() |
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| 177 | |||
| 178 | /** |
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| 179 | * {@inheritdoc} |
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| 180 | */ |
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| 181 | final public function floor() |
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| 187 | |||
| 188 | /** |
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| 189 | * {@inheritdoc} |
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| 190 | */ |
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| 191 | final public function round($roundingMode) |
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| 197 | |||
| 198 | /** |
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| 199 | * {@inheritdoc} |
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| 200 | */ |
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| 201 | final public function absolute() |
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| 207 | |||
| 208 | 10 | final public static function __callStatic($unit, $args) |
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| 209 | { |
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| 210 | 10 | return static::create($unit, $args[0]); |
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| 211 | } |
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| 212 | |||
| 213 | 10 | public static function create($unit, $quantity) |
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| 217 | |||
| 218 | /** |
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| 219 | * Returns unit for given unit name. |
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| 220 | * The only function to change in child classes. |
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| 221 | * XXX Should be defined as abstract but `abstract static` is not supported in PHP5. |
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| 222 | * @param string $name |
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| 223 | * @throws InvalidConfigException |
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| 224 | * @return UnitInterface |
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| 225 | */ |
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| 226 | protected static function findUnit($unit) |
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| 230 | |||
| 231 | /** |
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| 232 | * {@inheritdoc} |
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| 233 | * @return array |
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| 234 | */ |
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| 235 | public function jsonSerialize() |
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| 242 | |||
| 243 | } |
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| 244 |
Loading history...
If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.