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https://github.com/friendica/friendica
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90 lines
3 KiB
Markdown
90 lines
3 KiB
Markdown
Friendica strategy Hooks
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===========================================
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* [Home](help)
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## Strategy hooks
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This type of hook is based on the [Strategy Design Pattern](https://refactoring.guru/design-patterns/strategy).
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A strategy class defines a possible implementation of a given interface based on a unique name.
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Every name is possible as long as it's unique and not `null`.
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Using an empty name (`''`) is possible as well and should be used as the "default" implementation.
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To register a strategy, use the [`ICanRegisterInstance`](../src/Core/Hooks/Capability/ICanRegisterInstances.php) interface.
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After registration, a caller can automatically create this instance with the [`ICanCreateInstances`](../src/Core/Hooks/Capability/ICanCreateInstances.php) interface and the chosen name.
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This is useful in case there are different, possible implementations for the same purpose, like for logging, locking, caching, ...
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Normally, a config entry is used to choose the right implementation at runtime.
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And if no config entry is set, the "default" implementation should be used.
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### Example
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```php
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interface ExampleInterface
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{
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public function testMethod();
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}
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public class ConcreteClassA implements ExampleInterface
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{
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public function testMethod()
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{
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echo "concrete class A";
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}
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}
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public class ConcreteClassB implements ExampleInterface
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{
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public function testMethod()
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{
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echo "concrete class B";
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}
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}
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/** @var \Friendica\Core\Hooks\Capability\ICanRegisterStrategies $instanceRegister */
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$instanceRegister->registerStrategy(ExampleInterface::class, ConcreteClassA::class, 'A');
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$instanceRegister->registerStrategy(ExampleInterface::class, ConcreteClassB::class, 'B');
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/** @var \Friendica\Core\Hooks\Capability\ICanCreateInstances $instanceManager */
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/** @var ConcreteClassA $concreteClass */
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$concreteClass = $instanceManager->create(ExampleInterface::class, 'A');
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$concreteClass->testMethod();
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// output:
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// "concrete class A";
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```
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## hooks.config.php
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To avoid registering all strategies manually inside the code, Friendica introduced the [`hooks.config.php`](../static/hooks.config.php) file.
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There, you can register all kind of strategies in one file.
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### [`HookType::STRATEGY`](../src/Core/Hooks/Capability/HookType.php)
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For each given interface, a list of key-value pairs can be set, where the key is the concrete implementation class and the value is an array of unique names.
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### Example
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```php
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use Friendica\Core\Hooks\Capability\BehavioralHookType as H;
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return [
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H::STRATEGY => [
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ExampleInterface::class => [
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ConcreteClassA::class => ['A'],
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ConcreteClassB::class => ['B'],
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],
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],
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];
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```
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## Addons
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The hook logic is useful for decoupling the Friendica core logic, but its primary goal is to modularize Friendica in creating addons.
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Therefor you can either use the interfaces directly as shown above, or you can place your own `hooks.config.php` file inside a `static` directory directly under your addon core directory.
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Friendica will automatically search these config files for each **activated** addon and register the given hooks.
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