Add LazyCollection@remember method

laravel · Oct 28, 2019 · 54ae1cc · 54ae1cc
1 parent 0634709
commit 54ae1cc
Show file tree

Hide file tree

Showing 3 changed files with 117 additions and 0 deletions.
diff --git a/src/Illuminate/Support/LazyCollection.php b/src/Illuminate/Support/LazyCollection.php
@@ -109,6 +109,42 @@ public function eager()
         return new static($this->all());
     }
 
+    /**
+     * Cache values as they're enumerated.
+     *
+     * @return static
+     */
+    public function remember()
+    {
+        $iterator = $this->getIterator();
+
+        $iteratorIndex = 0;
+
+        $cache = [];
+
+        return new static(function () use ($iterator, &$iteratorIndex, &$cache) {
+            for ($index = 0; true; $index++) {
+                if (array_key_exists($index, $cache)) {
+                    yield $cache[$index][0] => $cache[$index][1];
+
+                    continue;
+                }
+
+                if ($iteratorIndex < $index) {
+                    $iterator->next();
+
+                    $iteratorIndex++;
+                }
+
+                if (! $iterator->valid()) break;
+
+                $cache[$index] = [$iterator->key(), $iterator->current()];
+
+                yield $cache[$index][0] => $cache[$index][1];
+            }
+        });
+    }
+
     /**
      * Get the average value of a given key.
      *

diff --git a/tests/Support/SupportLazyCollectionIsLazyTest.php b/tests/Support/SupportLazyCollectionIsLazyTest.php
@@ -763,6 +763,27 @@ public function testRejectIsLazy()
         });
     }
 
+    public function testRememberIsLazy()
+    {
+        $this->assertDoesNotEnumerate(function ($collection) {
+            $collection->remember();
+        });
+
+        $this->assertEnumeratesOnce(function ($collection) {
+            $collection = $collection->remember();
+
+            $collection->all();
+            $collection->all();
+        });
+
+        $this->assertEnumerates(5, function ($collection) {
+            $collection = $collection->remember();
+
+            $collection->take(5)->all();
+            $collection->take(5)->all();
+        });
+    }
+
     public function testReplaceIsLazy()
     {
         $this->assertDoesNotEnumerate(function ($collection) {

diff --git a/tests/Support/SupportLazyCollectionTest.php b/tests/Support/SupportLazyCollectionTest.php
@@ -80,6 +80,66 @@ public function testEager()
         $this->assertSame([1, 2, 3, 4, 5], $data->all());
     }
 
+    public function testRemember()
+    {
+        $source = [1, 2, 3, 4];
+
+        $collection = LazyCollection::make(function () use (&$source) {
+            yield from $source;
+        })->remember();
+
+        $this->assertSame([1, 2, 3, 4], $collection->all());
+
+        $source = [];
+
+        $this->assertSame([1, 2, 3, 4], $collection->all());
+    }
+
+    public function testRememberWithTwoRunners()
+    {
+        $source = [1, 2, 3, 4];
+
+        $collection = LazyCollection::make(function () use (&$source) {
+            yield from $source;
+        })->remember();
+
+        $a = $collection->getIterator();
+        $b = $collection->getIterator();
+
+        $this->assertEquals(1, $a->current());
+        $this->assertEquals(1, $b->current());
+
+        $b->next();
+
+        $this->assertEquals(1, $a->current());
+        $this->assertEquals(2, $b->current());
+
+        $b->next();
+
+        $this->assertEquals(1, $a->current());
+        $this->assertEquals(3, $b->current());
+
+        $a->next();
+
+        $this->assertEquals(2, $a->current());
+        $this->assertEquals(3, $b->current());
+
+        $a->next();
+
+        $this->assertEquals(3, $a->current());
+        $this->assertEquals(3, $b->current());
+
+        $a->next();
+
+        $this->assertEquals(4, $a->current());
+        $this->assertEquals(3, $b->current());
+
+        $b->next();
+
+        $this->assertEquals(4, $a->current());
+        $this->assertEquals(4, $b->current());
+    }
+
     public function testTapEach()
     {
         $data = LazyCollection::times(10);