面向对象之组合

组合的概念

一个类的对象具有某一个属性，该属性的值是来自于另一个类的对象，称之为组合，组合也是用来解决类与类之间代码冗余的问题

组合的使用

在继承中，举了一个属性查找顺序方式一的例子，最终的实现成果以下

class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id): People.__init__(self, name, age, gender) self.stu_id = stu_id def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level, salary): People.__init__(self, name, age, gender) self.level = level self.salary = salary def score(self, stu, num): print('教师%s给学生%s打%s分' %(self.name, stu.name, num)) stu.num = num stu = Student('qiu', 22, 'male') tea = Teacher('xi', 20, 'male', 10, 3000)

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如今学生有课程信息，课程价格，课程周期，教师也有相同的信息，因而添加相应的数据属性，注意这里不能将这些信息放到对应的类里面，假如我将一门课程放入学生类，那当我实例化一个学生对象时，他只能学习这门课程，若是我有多个课程呢？因此这些信息是对象独有的，并非公有的

class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id, course_name, course_period, course_price): People.__init__(self, name, age, gender) self.stu_id = stu_id self.course_name = course_name self.course_period = course_period self.course_price = course_price def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level, course_name, course_period, course_price): People.__init__(self, name, age, gender) self.level = level self.course_name = course_name self.course_period = course_period self.course_price = course_price def score(self, stu, num): stu.score = num print('教师%s给学生%s打%s分' % (self.name, stu.name, num))

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但这样写出来你会发现，代码又有重复部分了，能够考虑将课程信息放到父类 People，但并不合理，并非全部 “湫兮如风学院” 的人都有这些课程信息，若是还有个管理员，他并不须要这些课程信息。还有教师与学生都属于 “湫兮如风学院” 的人，这是一个从属关系，可使用继承，但课程与老师、课程与学生之间没有从属关系，仅仅是老师和学生有课程这种属性。因此此时考虑再定义一个类，用来存放课程信息，并实例化出两门课程

class Course(): def __init__(self, course_name, course_price, course_period): self.course_name = course_name self.course_price = course_price self.course_period = course_period class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id): People.__init__(self, name, age, gender) self.stu_id = stu_id def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level): People.__init__(self, name, age, gender) self.level = level def score(self, stu, num): stu.score = num print('教师%s给学生%s打%s分' % (self.name, stu.name, num)) python = Course('Python全栈开发', '5 months', 3000) linux = Course('linux运维', '5 months', 2000)

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这时课程与学生、课程与老师之间尚未创建关系，因此要作创建关系的操做

class Course(): def __init__(self, course_name, course_price, course_period): self.course_name = course_name self.course_price = course_price self.course_period = course_period class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id): People.__init__(self, name, age, gender) self.stu_id = stu_id def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level): People.__init__(self, name, age, gender) self.level = level def score(self, stu, num): stu.score = num print('教师%s给学生%s打%s分' % (self.name, stu.name, num)) # 建立课程
python = Course('Python全栈开发', '5 months', 3000) linux = Course('linux运维', '5 months', 2000) # 建立学生和老师
stu1 = Student('夕颜', 19, 'male', 1001) tea1 = Teacher('东风', 19, 'female', 10) # 将学生、老师与课程对象关联
stu1.course = python tea1.course = linux # 查看学生和老师的课程，
print(stu1.course) print(tea1.course) # 运行
<__main__.Course object at 0x000002081E998D68>
<__main__.Course object at 0x000002081E998DA0>

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创建了关系，即可以查看学生与老师的课程信息，但上面的输出操做并不能查看到学生选了哪门课程，老师选了哪门课程，查看的并非课程的详细信息，因而须要进一步访问学生课程信息的课程名、课程周期、课程价格，一样老师的课程信息也须要进一步才能访问

class Course(): def __init__(self, course_name, course_period, course_price, ): self.course_name = course_name self.course_price = course_price self.course_period = course_period class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id): People.__init__(self, name, age, gender) self.stu_id = stu_id def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level): People.__init__(self, name, age, gender) self.level = level def score(self, stu, num): stu.score = num print('教师%s给学生%s打%s分' % (self.name, stu.name, num)) # 建立课程
python = Course('Python全栈开发', '5个月', 3000) linux = Course('linux运维', '5个月', 2000) # 建立学生和老师
stu1 = Student('夕颜', 19, 'male', 1001) tea1 = Teacher('东风', 19, 'female', 10) # 将学生、老师与课程对象关联
stu1.course = python tea1.course = linux # 查看学生和老师的课程
print(stu1.course.course_name, stu1.course.course_period, stu1.course.course_price) print(tea1.course.course_name, tea1.course.course_period, tea1.course.course_price) # 运行
Python全栈开发 5个月 3000 linux运维 5个月 2000

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这样确实可以访问到课程的详细信息，可是你会发现，我作了一样的事情，每次都要先去访问课程才能访问到课程的详细信息，因而能够考虑将课程的详细信息做为一个功能（函数），每次访问经过学生的课程或老师的课程去访问，也就是说把学生的课程或老师的课程看成参数传入这个函数，而后再去访问课程的详细信息

class Course(): def __init__(self, course_name, course_period, course_price, ): self.course_name = course_name self.course_price = course_price self.course_period = course_period class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id): People.__init__(self, name, age, gender) self.stu_id = stu_id def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level): People.__init__(self, name, age, gender) self.level = level def score(self, stu, num): stu.score = num print('教师%s给学生%s打%s分' % (self.name, stu.name, num)) # 建立课程
python = Course('Python全栈开发', '5个月', 3000) linux = Course('linux运维', '5个月', 2000) # 建立学生和老师
stu1 = Student('夕颜', 19, 'male', 1001) tea1 = Teacher('东风', 19, 'female', 10) # 将学生、老师与课程对象关联
stu1.course = python tea1.course = linux def tell_info(course_obj): print(course_obj.course_name, course_obj.course_period, course_obj.course_price) # 查看学生和老师课程的详细信息
tell_info(stu1.course) tell_info(tea1.course)

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这时便不须要作一样的事情了，每次只须要传入一个课程对象，可是在调用的时候都是手动去传入课程对象，我如今想实现的是让它自动传入一个课程对象，因而将它放入课程类中，经过 self 自动传入，而后课程对象就能够调用这个功能去查看课程的相关信息

class Course(): def __init__(self, course_name, course_period, course_price, ): self.course_name = course_name self.course_price = course_price self.course_period = course_period def tell_info(self): print("课程名: %s | 课程周期: %s | 课程价格: %s"
              %(self.course_name, self.course_period, self.course_price)) class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id): People.__init__(self, name, age, gender) self.stu_id = stu_id def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level): People.__init__(self, name, age, gender) self.level = level def score(self, stu, num): stu.score = num print('教师%s给学生%s打%s分' % (self.name, stu.name, num)) # 建立课程
python = Course('Python全栈开发', '5个月', 3000) linux = Course('linux运维', '5个月', 2000) # 经过课程对象去查看课程的详细信息
python.tell_info() linux.tell_info() # 建立学生和老师
stu1 = Student('夕颜', 19, 'male', 1001) tea1 = Teacher('东风', 19, 'female', 10) # 将学生、老师与课程对象关联
stu1.course = python tea1.course = linux

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学生和老师也能够经过所选的课程去访问该课程的详细信息

class Course(): def __init__(self, course_name, course_period, course_price, ): self.course_name = course_name self.course_price = course_price self.course_period = course_period def tell_info(self): print("课程名: %s | 课程周期: %s | 课程价格: %s"
              %(self.course_name, self.course_period, self.course_price)) class People(): school = '湫兮如风学院'

    def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender class Student(People): def __init__(self, name, age, gender, stu_id): People.__init__(self, name, age, gender) self.stu_id = stu_id def choose_course(self): print('%s正在选课' %self.name) class Teacher(People): def __init__(self, name, age, gender, level): People.__init__(self, name, age, gender) self.level = level def score(self, stu, num): stu.score = num print('教师%s给学生%s打%s分' % (self.name, stu.name, num)) # 建立课程
python = Course('Python全栈开发', '5个月', 3000) linux = Course('linux运维', '5个月', 2000) # 经过课程对象去查看课程的详细信息 # python.tell_info() # linux.tell_info()

# 建立学生和老师
stu1 = Student('夕颜', 19, 'male', 1001) tea1 = Teacher('东风', 19, 'female', 10) # 将学生、老师与课程对象关联
stu1.course = python tea1.course = linux # 学生和老师所选课程的详细信息
stu1.course.tell_info() tea1.course.tell_info() # 运行
课程名: Python全栈开发 | 课程周期: 5个月 | 课程价格: 3000 课程名: linux运维 | 课程周期: 5个月 | 课程价格: 2000

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以上就是组合的应用，让一个类的对象具有一个属性，这个属性的值来自于另一个类的对象，这就是把两个类组合到一块儿