Some code cleanup, and added the value cache.

src/Behaviours/Cacheable.php

@@ -22,6 +22,14 @@ trait Cacheable
      */
     abstract private function configuration(): array;
 
+    /**
+     * Template method for setting up the CacheConfig object.
+     */
+    protected function config($relationName, $aggregateField): CacheConfig
+    {
+        return new CacheConfig($relationName, $aggregateField);
+    }
+
     /**
      * Helper method for easier use of the implementing classes.
      */
@@ -101,9 +109,9 @@ public function rebuildCacheRecord(CacheConfig $config, Model $model, $command):
     /**
      * Update the cache value for the model.
      */
-    protected function updateCacheValue(Model $model, CacheConfig $config, int $amount): void
+    protected function updateCacheValue(Model $model, CacheConfig $config, $value): void
     {
-        $model->{$config->aggregateField} = $model->{$config->aggregateField} + $amount;
+        $model->{$config->aggregateField} = $model->{$config->aggregateField} + $value;
         $model->save();
     }
 }

src/Behaviours/CountCache/CountCache.php

@@ -71,12 +71,4 @@ public function decrement(): void
             $this->updateCacheValue($config->relatedModel($this->model), $config, -1);
         });
     }
-
-    /**
-     * Takes a registered counter cache, and setups up defaults.
-     */
-    protected function config($key, string $value): CacheConfig
-    {
-        return new CacheConfig($key, $value);
-    }
 }

src/Behaviours/CountCache/HasCounts.php

@@ -4,7 +4,7 @@
 
 trait HasCounts
 {
-    public static function bootHasCounts()
+    public static function bootHasCounts(): void
     {
         static::observe(Observer::class);
     }

src/Behaviours/SumCache/HasSums.php

@@ -4,7 +4,7 @@
 
 trait HasSums
 {
-    public static function bootHasSums()
+    public static function bootHasSums(): void
     {
         static::observe(Observer::class);
     }

src/Behaviours/SumCache/SumCache.php

@@ -68,13 +68,13 @@ public function update(): void
     /**
      * Takes a registered sum cache, and setups up defaults.
      */
-    protected function config($relation, string|array $sourceField): CacheConfig
+    protected function config($relationName, $sourceField): CacheConfig
     {
         $keys = array_keys($sourceField);
 
         $aggregateField = $keys[0];
         $sourceField = $sourceField[$aggregateField];
 
-        return new CacheConfig($relation, $aggregateField, $sourceField);
+        return new CacheConfig($relationName, $aggregateField, $sourceField);
     }
 }

src/Behaviours/ValueCache/HasValues.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Eloquence\Behaviours\ValueCache;
+
+trait HasValues
+{
+    public static function bootHasValues(): void
+    {
+        static::observe(Observer::class);
+    }
+
+    public static function rebuildValueCache(): void
+    {
+        ValueCache::for(new self())->rebuild();
+    }
+}

src/Behaviours/ValueCache/Observer.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Eloquence\Behaviours\ValueCache;
+
+class Observer
+{
+    public function created($model): void
+    {
+        ValueCache::for($model)->updateRelated(true);
+    }
+
+    public function updated($model): void
+    {
+        ValueCache::for($model)->updateRelated(false);
+    }
+}

src/Behaviours/ValueCache/ValueCache.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace Eloquence\Behaviours\ValueCache;
+
+use Eloquence\Behaviours\Cacheable;
+use Eloquence\Behaviours\CacheConfig;
+use Illuminate\Database\Eloquent\Model;
+
+class ValueCache
+{
+    use Cacheable;
+
+    private function __construct(private Model $model)
+    {
+    }
+
+    protected function config($relationName, $sourceField): CacheConfig
+    {
+        $keys = array_keys($sourceField);
+
+        $aggregateField = $keys[0];
+        $sourceField = $sourceField[$aggregateField];
+
+        return new CacheConfig($relationName, $aggregateField, $sourceField);
+    }
+
+    public function rebuild()
+    {
+
+    }
+
+    public function updateRelated(bool $new): void
+    {
+        $this->apply(function(CacheConfig $config) use ($new) {
+            $foreignKey = $config->foreignKeyName($this->model);
+
+            // We only do work if the model previously existed and the source field has changed, or the model was newly created in the database.
+            if (!($new || $this->model->wasChanged($config->sourceField))) {
+                return;
+            }
+
+            $relatedModel = $config->emptyRelatedModel($this->model)->find($this->model->$foreignKey);
+
+            $relatedModel->{$config->aggregateField} = $this->model->{$config->sourceField};
+            $relatedModel->save();
+        });
+    }
+
+    private function configuration(): array
+    {
+        return $this->reflect(ValuedBy::class, function (array $config) {
+            return [$config['name'] => [$config['attribute']->as => $config['attribute']->from]];
+        });
+    }
+}

src/Behaviours/ValueCache/ValuedBy.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Eloquence\Behaviours\ValueCache;
+
+use Attribute;
+
+#[Attribute(Attribute::TARGET_METHOD)]
+class ValuedBy
+{
+    public function __construct(readonly string $from, readonly ?string $as)
+    {
+    }
+}

tests/Acceptance/AcceptanceTestCase.php

@@ -56,6 +56,7 @@ private function migrate()
             $table->integer('user_id')->nullable();
             $table->string('slug')->nullable();
             $table->integer('comment_count')->default(0);
+            $table->dateTime('publish_at')->nullable();
             $table->timestamps();
         });
 
@@ -85,6 +86,7 @@ private function migrate()
             $table->increments('id');
             $table->integer('post_count')->default(0);
             $table->integer('total_comments')->default(0);
+            $table->dateTime('last_activity_at')->nullable();
             $table->timestamps();
         });
     }

tests/Acceptance/ModelTest.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Tests\Acceptance;
+
+class ModelTest
+{
+
+}

tests/Acceptance/Models/Post.php

@@ -7,6 +7,8 @@
 use Eloquence\Behaviours\HasSlugs;
 use Eloquence\Behaviours\SumCache\HasSums;
 use Eloquence\Behaviours\SumCache\SummedBy;
+use Eloquence\Behaviours\ValueCache\HasValues;
+use Eloquence\Behaviours\ValueCache\ValuedBy;
 use Illuminate\Database\Eloquent\Factories\Factory;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
@@ -19,10 +21,12 @@ class Post extends Model
     use HasCounts;
     use HasFactory;
     use HasSums;
+    use HasValues;
 
     protected $fillable = [
         'user_id',
         'category_id',
+        'publish_at',
     ];
 
     #[CountedBy(as: 'post_count')]
@@ -38,6 +42,7 @@ public function slugStrategy()
 
     #[CountedBy]
     #[SummedBy(from: 'comment_count', as: 'total_comments')]
+    #[ValuedBy(from: 'publish_at', as: 'last_activity_at')]
     public function category(): BelongsTo
     {
         return $this->belongsTo(Category::class);

tests/Acceptance/ValueCacheTest.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Tests\Acceptance;
+
+use Tests\Acceptance\Models\Category;
+use Tests\Acceptance\Models\Post;
+
+class ValueCacheTest extends AcceptanceTestCase
+{
+    function test_values_from_related_models_are_cached()
+    {
+        $category = Category::factory()->create();
+
+        $this->assertNull($category->last_activity_at);
+
+        $post = Post::factory()->create(['category_id' => $category->id, 'publish_at' => now()->subDays(mt_rand(1, 10))]);
+
+        $this->assertEquals($category->fresh()->last_activity_at, $post->publish_at);
+    }
+}