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Dominik Liebler
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Refactored example of Proxy pattern
1 parent a494c07 commit ea85485

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10 files changed

+197
-413
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10 files changed

+197
-413
lines changed

‎Structural/Proxy/BankAccount.php

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<?php
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namespace DesignPatterns\Structural\Proxy;
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interface BankAccount
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{
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public function deposit(int $amount);
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public function getBalance(): int;
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}

‎Structural/Proxy/BankAccountProxy.php

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<?php
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namespace DesignPatterns\Structural\Proxy;
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class BankAccountProxy extends HeavyBankAccount implements BankAccount
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{
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/**
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* @var int
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*/
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private $balance;
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public function getBalance(): int
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{
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// because calculating balance is so expensive,
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// the usage of BankAccount::getBalance() is delayed until it really is needed
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// and will not be calculated again for this instance
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if ($this->balance === null) {
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$this->balance = parent::getBalance();
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}
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return $this->balance;
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}
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}

‎Structural/Proxy/HeavyBankAccount.php

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<?php
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namespace DesignPatterns\Structural\Proxy;
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class HeavyBankAccount implements BankAccount
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{
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/**
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* @var int[]
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*/
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private $transactions = [];
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public function deposit(int $amount)
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{
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$this->transactions[] = $amount;
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}
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public function getBalance(): int
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{
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// this is the heavy part, imagine all the transactions even from
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// years and decades ago must be fetched from a database or web service
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// and the balance must be calculated from it
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return array_sum($this->transactions);
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}
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}

‎Structural/Proxy/README.rst

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You can also find this code on `GitHub`_
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Record.php
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BankAccount.php
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.. literalinclude:: Record.php
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.. literalinclude:: BankAccount.php
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:language: php
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:linenos:
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RecordProxy.php
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HeavyBankAccount.php
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.. literalinclude:: RecordProxy.php
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.. literalinclude:: HeavyBankAccount.php
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:language: php
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:linenos:
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BankAccountProxy.php
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.. literalinclude:: BankAccountProxy.php
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:language: php
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:linenos:
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‎Structural/Proxy/Record.php

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This file was deleted.

‎Structural/Proxy/RecordProxy.php

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This file was deleted.

‎Structural/Proxy/Tests/ProxyTest.php

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namespace DesignPatterns\Structural\Proxy\Tests;
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use DesignPatterns\Structural\Proxy\RecordProxy;
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use DesignPatterns\Structural\Proxy\BankAccountProxy;
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use PHPUnit\Framework\TestCase;
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class ProxyTest extends TestCase
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{
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public function testWillSetDirtyFlagInProxy()
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public function testProxyWillOnlyExecuteExpensiveGetBalanceOnce()
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{
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$recordProxy = new RecordProxy([]);
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$recordProxy->username = 'baz';
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$bankAccount = new BankAccountProxy();
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$bankAccount->deposit(30);
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$this->assertTrue($recordProxy->isDirty());
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}
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// this time balance is being calculated
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$this->assertEquals(0, $bankAccount->getBalance());
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public function testProxyIsInstanceOfRecord()
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{
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$recordProxy = new RecordProxy([]);
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$recordProxy->username = 'baz';
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// inheritance allows for BankAccountProxy to behave to an outsider exactly like ServerBankAccount
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$bankAccount->deposit(50);
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$this->assertInstanceOf(RecordProxy::class, $recordProxy);
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// this time the previously calculated balance is returned again without re-calculating it
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$this->assertEquals(0, $bankAccount->getBalance());
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}
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}

‎Structural/Proxy/uml/Proxy.uml

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<?xml version="1.0" encoding="UTF-8"?>
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<Diagram>
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<ID>PHP</ID>
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<OriginalElement>\DesignPatterns\Structural\Proxy\Record</OriginalElement>
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<nodes>
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<node x="4.0" y="0.0">\DesignPatterns\Structural\Proxy\Record</node>
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<node x="0.0" y="159.0">\DesignPatterns\Structural\Proxy\RecordProxy</node>
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</nodes>
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<notes />
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<edges>
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<edge source="\DesignPatterns\Structural\Proxy\RecordProxy" target="\DesignPatterns\Structural\Proxy\Record">
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<point x="0.0" y="-54.5" />
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<point x="0.0" y="54.5" />
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</edge>
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</edges>
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<settings layout="Hierarchic Group" zoom="1.0" x="81.0" y="134.0" />
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<SelectedNodes>
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<node>\DesignPatterns\Structural\Proxy\Record</node>
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</SelectedNodes>
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<Categories>
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<Category>Fields</Category>
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<Category>Constants</Category>
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<Category>Constructors</Category>
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<Category>Methods</Category>
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</Categories>
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<VISIBILITY>private</VISIBILITY>
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</Diagram>
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<?xml version="1.0" encoding="UTF-8"?>
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<Diagram>
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<ID>PHP</ID>
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<OriginalElement>\DesignPatterns\Structural\Proxy\BankAccount</OriginalElement>
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<nodes>
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<node x="7.5" y="282.0">\DesignPatterns\Structural\Proxy\BankAccountProxy</node>
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<node x="-58.0" y="123.0">\DesignPatterns\Structural\Proxy\HeavyBankAccount</node>
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<node x="45.0" y="0.0">\DesignPatterns\Structural\Proxy\BankAccount</node>
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</nodes>
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<notes />
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<edges>
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<edge source="\DesignPatterns\Structural\Proxy\HeavyBankAccount" target="\DesignPatterns\Structural\Proxy\BankAccount">
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<point x="0.0" y="-48.0" />
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<point x="21.5" y="98.0" />
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<point x="84.75" y="98.0" />
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<point x="-39.75" y="36.5" />
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</edge>
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<edge source="\DesignPatterns\Structural\Proxy\BankAccountProxy" target="\DesignPatterns\Structural\Proxy\BankAccount">
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<point x="37.5" y="-37.0" />
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<point x="120.0" y="243.0" />
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<point x="164.5" y="243.0" />
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<point x="164.5" y="161.0" />
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<point x="165.25" y="105.0" />
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<point x="39.75" y="36.5" />
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</edge>
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<edge source="\DesignPatterns\Structural\Proxy\BankAccountProxy" target="\DesignPatterns\Structural\Proxy\HeavyBankAccount">
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<point x="-37.5" y="-37.0" />
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<point x="45.0" y="247.0" />
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<point x="21.5" y="247.0" />
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<point x="0.0" y="48.0" />
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</edge>
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</edges>
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<settings layout="Hierarchic Group" zoom="1.0" x="73.0" y="178.0" />
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<SelectedNodes />
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<Categories>
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<Category>Fields</Category>
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<Category>Constants</Category>
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<Category>Constructors</Category>
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<Category>Methods</Category>
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</Categories>
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<VISIBILITY>private</VISIBILITY>
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</Diagram>
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‎Structural/Proxy/uml/uml.png

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