protected function getSortableColumns()
    {
        if ($this->sortableColumns !== null) {
            return $this->sortableColumns;
        }

        $columns = $this->getColumns();
        $sortable = array_filter($columns, function ($column) {
            return $column->sortable;
        });

        return $this->sortableColumns = $sortable;
    }
protected function getSortableColumns()
    {
        if ($this->sortableColumns !== null) {
            return $this->sortableColumns;
        }

        $columns = $this->getColumns();
        $sortable = array_filter($columns, function ($column) {
            return $column->sortable;
        });

        return $this->sortableColumns = $sortable;
    }
protected function getSortableColumns ( ) { if ( $ this -> sortableColumns !== null ) { return $ this -> sortableColumns ; } $ columns = $ this -> getColumns ( ) ; $ sortable = array_filter ( $ columns , function ( $ column ) { return $ column -> sortable ; } ) ; return $ this -> sortableColumns = $ sortable ; }
Returns a collection of columns which are sortable.
Returns a collection of columns which are sortable .