Dependency Inversion Principle

src/Contract/LoaderInterface.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace solid\Contract;
+
+interface LoaderInterface
+{
+    public function loadFile(): array;
+}

src/DataImporter.php

@@ -3,14 +3,14 @@
 namespace solid;
 
 use solid\Contract\ImportDataInterface;
-use solid\Loader\CsvLoader;
+use solid\Contract\LoaderInterface;
 
 class DataImporter
 {
     private ImportDataInterface $importer;
-    private CsvLoader $loader;
+    private LoaderInterface $loader;
 
-    public function __construct(ImportDataInterface $importer, CsvLoader $loader)
+    public function __construct(ImportDataInterface $importer, LoaderInterface $loader)
     {
         $this->importer = $importer;
         $this->loader = $loader;

src/Loader/CsvLoader.php

@@ -4,9 +4,11 @@
 
 namespace solid\Loader;
 
-class CsvLoader
+use solid\Contract\LoaderInterface;
+
+class CsvLoader implements LoaderInterface
 {
-    protected string $filename;
+    private string $filename;
 
     public function __construct(string $filename)
     {

src/Loader/JsonLoader.php

@@ -5,9 +5,17 @@
 namespace solid\Loader;
 
 use DateTimeImmutable;
+use solid\Contract\LoaderInterface;
 
-class JsonLoader extends CsvLoader
+class JsonLoader implements LoaderInterface
 {
+    private string $filename;
+
+    public function __construct(string $filename)
+    {
+        $this->filename = $filename;
+    }
+
     private function readFile(): array
     {
         return json_decode(file_get_contents($this->filename), true);