我是一个sitebuilder,我有一些表,并且可以根据该表总是构建一个类并创建它的一个对象吗?我有一个教师表(ID,USERNAME)和一个基于它的类得到了giveMark(),editMark()等.另一个是学生(ID,NAME)表,有getMarks(),getMissingHours()等.现在,因为那里有学生和老师之间的N:M关系,我有一个link_teacher_student(ID,TEACHED_ID,STUDENT_ID)表,而不是一个“帮助者”表.我应该为它创建类/对象吗?
解决方法:
不,你不应该有link_teacher_student表的对象. This is common thing to do in a RDBMS structure, but not in an OOP model. OOP模型中的相同关系是简单的:
class Teacher {
protected $students = array();
}
class Student {
protected $teachers = array();
}
然后,在获取教师或学生时,您将使用DataMapper初始化该数组,例如您的DAO将查询教师和join the students,然后Mapper将查询create Student objects并将其填充到教师的该数组中.
你可以做的是让$student或$teacher进入Repositories并给他们finder方法来查询查询表,例如
class Teacher
…
public function __construct($studentsRepository)
{
$this->students = $studentRepository;
}
public function getStudents()
{
return $this->students->findByTeacherId($this->id);
}
}
class StudentRepository
…
public function findByTeacherId($teacherId)
{
foreach ($this->dao->select('SELECT …', $teacherId) as $student) {
$students[] = $this->studentBuilder->build($student);
}
return $students;
}
}