# keyBy方法 以给定的键作为集合的键。如果多个项目具有相同的键，则只有最后一个项目会显示在新集合中。 ``` $collection = collect([ ['product_id' => 'prod-100', 'name' => 'desk'], ['product_id' => 'prod-200', 'name' => 'chair'], ]); $keyed = $collection->keyBy('product_id'); $keyed->all(); /* [ 'prod-100' => ['product_id' => 'prod-100', 'name' => 'Desk'], 'prod-200' => ['product_id' => 'prod-200', 'name' => 'Chair'], ] */ ``` 也可以传入一个回调方法，回调返回的值会作为该集合的键 ``` $keyed = $collection->keyBy(function ($item) { return strtoupper($item['product_id']); }); $keyed->all(); /* [ 'PROD-100' => ['product_id' => 'prod-100', 'name' => 'Desk'], 'PROD-200' => ['product_id' => 'prod-200', 'name' => 'Chair'], ] */ ```