## whenNotEmpty 方法当集合不为空时，将执行给定的回调函数： whenNotEmpty 方法当集合不为空时，将执行给定的回调函数： ``` $collection = collect(['michael', 'tom']); $collection->whenNotEmpty(function ($collection) { return $collection->push('adam'); }); $collection->all(); // ['michael', 'tom', 'adam'] $collection = collect(); $collection->whenNotEmpty(function ($collection) { return $collection->push('adam'); }); $collection->all(); // [] $collection = collect(); $collection->whenNotEmpty(function ($collection) { return $collection->push('adam'); }, function ($collection) { return $collection->push('taylor'); }); $collection->all(); // ['taylor'] ``` 与 whenNotEmpty 相反的方法，请查看 whenEmpty 方法