feat: add Field::getId() method

Author: danmichaelo

src/Fields/ControlField.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Scriptotek\Marc\Fields;
+
+class ControlField extends Field implements FieldInterface
+{
+    public function __toString()
+    {
+        return $this->field->getData();
+    }
+}

src/Record.php

@@ -127,6 +127,13 @@ public function getTitle()
         return $field ? $this->makeField('Title', $field) : null;
     }
 
+    public function getId()
+    {
+        $field = $this->record->getField('001');
+
+        return $field ? $this->makeField('ControlField', $field) : null;
+    }
+
     /*************************************************************************
      * Support methods
      *************************************************************************/

tests/IsbnFieldTest.php renamed to tests/FieldsTest.php

@@ -36,4 +36,16 @@ public function test020withoutA()
         $record = Record::fromString($source);
         $this->assertEquals(array(''), $record->isbns);
     }
+
+    public function testId()
+    {
+        $source = '<?xml version="1.0" encoding="UTF-8" ?>
+          <record xmlns="http://www.loc.gov/MARC21/slim">
+            <leader>99999cam a2299999 u 4500</leader>
+            <controlfield tag="001">98218834x</controlfield>
+          </record>';
+
+        $record = Record::fromString($source);
+        $this->assertEquals('98218834x', $record->id);
+    }
 }