1 | <?php namespace Indatus\Dispatcher\Scheduling; |
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14 | abstract class ScheduledCommand extends Command implements ScheduledCommandInterface |
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15 | { |
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16 | /** |
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17 | * Unfortunately, this has to be here for unit testing |
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18 | * |
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19 | * @var string |
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20 | */ |
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21 | protected $name = 'scheduledCommand'; |
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22 | |||
23 | /** |
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24 | * User to run the command as |
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25 | * |
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26 | * @return string Defaults to false to run as default user |
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27 | */ |
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28 | 1 | public function user() |
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32 | |||
33 | /** |
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34 | * Environment(s) under which the given command should run |
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35 | * |
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36 | * @return string|array |
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37 | */ |
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38 | 1 | public function environment() |
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42 | |||
43 | /** |
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44 | * Should this command be allowed to run when application is in maintenance mode |
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45 | * |
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46 | * @return boolean Defaults to false |
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47 | */ |
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48 | 1 | public function runInMaintenanceMode() |
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52 | } |
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53 |
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.