function Field($name)
    {
        if (!array_key_exists($name, $this->fields))
            throw new \InvalidArgumentException($name . ' is not a valid field for '. $this->name);
        
        return $this->fields[$name];
    }
function Field($name)
    {
        if (!array_key_exists($name, $this->fields))
            throw new \InvalidArgumentException($name . ' is not a valid field for '. $this->name);
        
        return $this->fields[$name];
    }
function Field ( $ name ) { if ( ! array_key_exists ( $ name , $ this -> fields ) ) throw new \ InvalidArgumentException ( $ name . ' is not a valid field for ' . $ this -> name ) ; return $ this -> fields [ $ name ] ; }
Gets the Field with given name. Alias is NOT allowed.
@param string $name The name of the desired field
@return Field
@throws \InvalidArgumentException if field doesn't belong to the table.
Gets the Field with given name . Alias is NOT allowed .