From bc7bf5265b1607c9af466c8092f9d4ef05096afd Mon Sep 17 00:00:00 2001
From: Roman Schmid <bummzack@gmail.com>
Date: Tue, 28 Jun 2022 09:29:32 +0200
Subject: [PATCH 1/5] fix: Deal with DataObjects or Int values, so that the
 correct value is shown with has_one

---
 src/TagField.php | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/TagField.php b/src/TagField.php
index 177ab23..7e45d46 100644
--- a/src/TagField.php
+++ b/src/TagField.php
@@ -402,6 +402,14 @@ class TagField extends MultiSelectField
             return $values->column($this->getTitleField());
         }
 
+        if ($values instanceof DataObject && $values->exists()) {
+            return [$values->ID];
+        }
+
+        if (is_int($values)) {
+            return [$values];
+        }
+
         return [trim((string) $values)];
     }
 

From e34d6e4898ff162b76e612eb39bf33a3f2e248ed Mon Sep 17 00:00:00 2001
From: Roman Schmid <bummzack@gmail.com>
Date: Mon, 4 Jul 2022 16:10:02 +0200
Subject: [PATCH 2/5] fix: Use the title-field for has_one DataObject relations

---
 src/TagField.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/TagField.php b/src/TagField.php
index 7e45d46..c8df287 100644
--- a/src/TagField.php
+++ b/src/TagField.php
@@ -403,7 +403,7 @@ class TagField extends MultiSelectField
         }
 
         if ($values instanceof DataObject && $values->exists()) {
-            return [$values->ID];
+            return [$values->getField($this->getTitleField())];
         }
 
         if (is_int($values)) {

From 560a1398ab9b9a947d962afc63fb37421ff92bd5 Mon Sep 17 00:00:00 2001
From: Roman Schmid <bummzack@gmail.com>
Date: Mon, 25 Jul 2022 16:49:23 +0200
Subject: [PATCH 3/5] fix: Do not use `getField` to allow for field fallback
 values

---
 src/TagField.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/TagField.php b/src/TagField.php
index c8df287..80df94e 100644
--- a/src/TagField.php
+++ b/src/TagField.php
@@ -403,7 +403,7 @@ class TagField extends MultiSelectField
         }
 
         if ($values instanceof DataObject && $values->exists()) {
-            return [$values->getField($this->getTitleField())];
+            return [$values->{$this->getTitleField()}];
         }
 
         if (is_int($values)) {

From 8da9f83cde9976d5acb5155a03fcd7b0b6f0848b Mon Sep 17 00:00:00 2001
From: Roman Schmid <bummzack@gmail.com>
Date: Tue, 26 Jul 2022 10:47:13 +0200
Subject: [PATCH 4/5] fix: Fall back to the `ID` if no title is given

---
 src/TagField.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/TagField.php b/src/TagField.php
index 80df94e..f280634 100644
--- a/src/TagField.php
+++ b/src/TagField.php
@@ -403,7 +403,7 @@ class TagField extends MultiSelectField
         }
 
         if ($values instanceof DataObject && $values->exists()) {
-            return [$values->{$this->getTitleField()}];
+            return [$values->{$this->getTitleField()} ?? $values->ID];
         }
 
         if (is_int($values)) {

From 3f1d65e88e6d8ceb2bc2e1e80050f5f720cd7bd9 Mon Sep 17 00:00:00 2001
From: Roman Schmid <bummzack@gmail.com>
Date: Thu, 28 Jul 2022 10:48:33 +0200
Subject: [PATCH 5/5] docs: Update readme with an example for `has_one`
 relations.

---
 readme.md | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/readme.md b/readme.md
index fccac8a..8ad0e31 100644
--- a/readme.md
+++ b/readme.md
@@ -73,6 +73,45 @@ $field = TagField::create(
 **Note:** This assumes you have imported the namespaces class, e.g. use
 SilverStripe\TagField\TagField;
 
+
+#### Has-One Relations
+
+You can also use the TagField to select values for `has_one` relations.
+Let's assume, that a `BlogPost` *has one* `BlogCategory`.
+
+```php
+class BlogCategory extends DataObject
+{
+    private static $db = [
+        'Title' => 'Varchar(200)',
+    ];
+}
+```
+
+```php
+use SilverStripe\ORM\DataObject;
+
+class BlogPost extends DataObject
+{
+    private static $has_one = [
+        'BlogCategory' => BlogCategory::class
+    ];
+}
+```
+
+```php
+$field = TagField::create(
+    'BlogCategoryID',
+    $this->fieldLabel('BlogCategory'),
+    BlogCategory::get()
+)
+    ->setIsMultiple(false)
+    ->setCanCreate(true);
+```
+
+**Note:** We're using the `ID` suffix for the field-name (eg. `BlogCategoryID` instead of `BlogCategory`) and
+only allow one value by setting `->setIsMultiple(false)`
+
 ### String Tags
 
 ```php