1 | <?php namespace nyx\console\input\parameter; |
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23 | abstract class Values extends core\collections\Map |
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24 | { |
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25 | /** |
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26 | * @var Definitions The Definitions of the Parameters that can be present in this collection. |
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27 | */ |
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28 | protected $definitions; |
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29 | |||
30 | /** |
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31 | * {@inheritdoc} |
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32 | * |
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33 | * @param Definitions $definition The Definitions of the Parameters that can be present in this collection. |
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34 | */ |
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35 | public function __construct(Definitions $definition, $items = null) |
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41 | |||
42 | /** |
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43 | * Returns the Definitions of the Parameters that can be present in this collection. |
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44 | * |
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45 | * @return Definitions |
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46 | */ |
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47 | public function definitions() : Definitions |
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51 | |||
52 | /** |
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53 | * {@inheritdoc} |
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54 | */ |
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55 | public function set($name, $value) : core\collections\interfaces\Map |
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73 | |||
74 | /** |
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75 | * Finalizes the Collection, populating it with Parameters that have not been explicitly set, but |
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76 | * have defined default values. |
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77 | * |
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78 | * @return $this |
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79 | */ |
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80 | public function finalize() : Values |
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95 | |||
96 | /** |
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97 | * Asserts a Parameter with the given name is defined for this collection and returns it. |
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98 | * |
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99 | * @param string $name The name of the Parameter. |
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100 | * @throws \OutOfBoundsException When no Parameter with the given name has been defined. |
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101 | * @return input\Parameter |
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102 | */ |
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103 | protected function assertIsDefined(string $name) : input\Parameter |
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112 | |||
113 | /** |
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114 | * {@inheritdoc} |
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115 | */ |
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116 | protected function derive($items) : core\collections\interfaces\Collection |
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120 | } |
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121 |
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_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.