Add support for callables in implode() method

README.md

@@ -464,8 +464,18 @@ have its elements in the same order for a given original collection and seed
 value. It will never return a different order for this combination.
 
 ### Implode
-The `implode()` method will take your collection and return a string with the items joined together with `$glue`
+The `implode()` method will take your collection and return a string with the
+items joined together with `$glue`
 ```php
 $collection = new Collection(['a', 'b']);
 $joined = $collection->implode(', '); // 'a, b'
 ```
+
+You may also pass an optional callable as the second argument which allows you
+to pick the specific properties from your collected objects when imploding:
+```php
+$collection = new Collection($users);
+$joined = $collection->implode(', ', function (User $user): string {
+    return $user->name();
+});
+```

src/Collection.php

@@ -421,11 +421,13 @@ public function shuffle(int $seed = null): self
      * Join collection elements together with a string
      *
      * @param string $glue
+     * @param callable $callable
      * @return static
      */
-    public function implode($glue = ""): string
+    public function implode($glue = "", callable $callable = null): string
     {
-        return implode($glue, $this->getArrayCopy());
+        $data = $callable ? $this->map($callable)->getArrayCopy() : $this->getArrayCopy();
+        return implode($glue, $data);
     }
 
     /**

tests/CollectionTest.php

@@ -726,6 +726,33 @@ public function itImplodesStrings(): void
         $this->assertSame('a, b', $collection->implode(', '));
     }
 
+    /** @test */
+    public function itImplodesObjects(): void
+    {
+        $newClass = function(string $foo) {
+            return new class($foo) {
+                private $foo;
+                public function __construct(string $foo) {
+                    $this->foo = $foo;
+                }
+                public function foo(): string {
+                    return $this->foo;
+                }
+            };
+        };
+        $collection = new Collection([
+            $newClass('foo'),
+            $newClass('bar'),
+            $newClass('baz')
+        ]);
+        $this->assertSame(
+            'foo, bar, baz',
+            $collection->implode(', ', function ($item) {
+                return $item->foo();
+            })
+        );
+    }
+