代码设计师更好地维护codeigniter

currently i'm using codeigniter then i see that can use the library db in 2 styles

$result =  $this->db->select($id)
                    ->select($field)
                    ->get('user');

and like this

$this->db->select($id)
$this->db->select($field)
$result = $this->db->get('user');

to a better designer which style is better, exist some pattern between developers php codeigniter

There is no Best way. Its all about your practice.
There are 3 Methods to code

Method 01

$result =  $this->db->select($id)
           ->select($field)
           ->get('user');

Method 02

$this->db->select($id)
$this->db->select($field)
$result = $this->db->get('user');

Method 03

$query = $this->db->query("SELECT * FROM user")
$result = $query->result_array();

You can use any way that you like. Code will execute in all this way.

Note : Method 01 and Method 02 from your Question and Method 03 is which i used.(Method 03 is tested and works well)