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PODifference between a function layer and an interface
 

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  1. PODifference between a function layer and an interface
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    <p>What's the difference between doing this:</p> <pre><code>class UserRepository extends DAO { public function GetAllUsers() { return $this-&gt;Select(); } public function GetUserById( $id ) { return $this-&gt;Select( $id ); } } class MockUserRepository extends MockDAO { public function GetAllUsers() { return $this-&gt;Select(); } public function GetUserById( $id ) { return $this-&gt;Select( $id ); } } class UserController { private $userRepository; function __Construct( $repo ) { $this-&gt;userRepository = $repo; } public function ListUsers() { $users = $this-&gt;userRepository-&gt;AnUndeclaredMethod(); // ... } } $repo = new MockUserRepository(); $controller = new UserController( $repo ); </code></pre> <p>and this:</p> <pre><code>interface IUserRepository { public function GetAllUsers(); public function GetUserById( $id ); } class UserRepository extends DAO implements IUserRepository { public function GetAllUsers() { return $this-&gt;Select(); } public function GetUserById( $id ) { return $this-&gt;Select( $id ); } } class MockUserRepository extends MockDAO implements IUserRepository { public function GetAllUsers() { return $this-&gt;SelectUsers(); } public function GetUserById( $id ) { return $this-&gt;SelectUsers( $id ); } } class UserController { private $userRepository; public function __Construct( IUserRepository $repo ) { $this-&gt;userRepository = $repo; } public function ListUsers() { $users = $this-&gt;userRepository-&gt;AnUndeclaredMethod(); // ... } } $repo = new MockUserRepository(); $controller = new UserController( $repo ); </code></pre> <p>If a function was used in the controller that wasn't declared in one of the repositories, it would throw an error anyway, why is it better to use an interface for this type of task? What do I benefit from?</p> <ol> <li>Is it all about the error? if you forget to implement one function you know must exist, it errors regardless of using it or not, is that the benefit of the interface?</li> <li>Is it about the fact that you may need 2 repositories for 2 data sources and so without knowing your application would just stop working if your controller called upon the function that wasn't implemented rather than straight away alerting you to the fact one of your repositories is not implementing the methods you have told it to in the interface? Once again, is it all about the errors?</li> </ol>
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    1. USJimmyt1988
    1. USJimmyt1988
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    1. CONot it's all about depending on contract, rather than on implementation. The consumer may only rely on presence of one method interface defines, which might be implemented by multiple various classes.
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      1. USzerkms
    2. COcontract? could you clarify?... (after your edit, not sure I understand what you mean).
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      1. USJimmyt1988
 

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