From 22efd3848e20b60cdc4173225ee84b2d86ab0be2 Mon Sep 17 00:00:00 2001
From: Stig Lindqvist <stojg.lindqvist@gmail.com>
Date: Wed, 19 Dec 2012 16:40:13 +1300
Subject: [PATCH] BUG Calling DataObject::relField() on a object with an empty
 relation list

This causes a 'Fatal error: Call to a member function hasMethod() on a non-object'.

This can happen when displaying a field in a gridfield on a belongs_to relationship.
---
 model/DataObject.php           | 30 ++++++++++++++++++------------
 tests/model/DataObjectTest.php |  3 +++
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/model/DataObject.php b/model/DataObject.php
index 27ae22fe0..ad4324e63 100644
--- a/model/DataObject.php
+++ b/model/DataObject.php
@@ -2619,27 +2619,33 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 	 * The path to the related field is specified with dot separated syntax (eg: Parent.Child.Child.FieldName)
 	 *
 	 * @param $fieldPath string
-	 * @return string
+	 * @return string | null - will return null on a missing value
 	 */
 	public function relField($fieldName) {
 		$component = $this;
 
+		// We're dealing with relations here so we traverse the dot syntax
 		if(strpos($fieldName, '.') !== false) {
-			$parts = explode('.', $fieldName);
-			$fieldName = array_pop($parts);
-
-			// Traverse dot syntax
-			foreach($parts as $relation) {
-				if($component instanceof SS_List) {
-					if(method_exists($component,$relation)) $component = $component->$relation();
-					else $component = $component->relation($relation);
-				} else {
+			$relations = explode('.', $fieldName);
+			$fieldName = array_pop($relations);
+			foreach($relations as $relation) {
+				// Bail if any of the below sets a $component to a null object
+				if($component instanceof SS_List && !method_exists($component, $relation)) {
+					$component = $component->relation($relation);
+				// Just call the method and hope for the best
+				} else { 
 					$component = $component->$relation();
 				}
 			}
 		}
-
-		if ($component->hasMethod($fieldName)) return $component->$fieldName();
+		
+		// Bail if the component is null
+		if(!$component) {
+			return null;
+		}
+		if($component->hasMethod($fieldName)) {
+			return $component->$fieldName();
+		}
 		return $component->$fieldName;
 	}
 
diff --git a/tests/model/DataObjectTest.php b/tests/model/DataObjectTest.php
index 6942dda02..ca4bb9a97 100644
--- a/tests/model/DataObjectTest.php
+++ b/tests/model/DataObjectTest.php
@@ -1091,6 +1091,9 @@ class DataObjectTest extends SapphireTest {
 		$player = $this->objFromFixture('DataObjectTest_Player', 'player2');
 		// Test that we can traverse more than once, and that arbitrary methods are okay
 		$this->assertEquals("Team 1", $player->relField('Teams.First.Title'));
+		
+		$newPlayer = new DataObjectTest_Player();
+		$this->assertNull($newPlayer->relField('Teams.First.Title'));
 	}
 
 	public function testRelObject() {