71 lines
1.8 KiB
Markdown
71 lines
1.8 KiB
Markdown
---
|
|
title: Builder
|
|
---
|
|
|
|
The builder is a design pattern that could abstract and decouple the creation of a very complex object.
|
|
|
|
## Builder in Python
|
|
Here is an example of Builder Pattern implementation in Python3.
|
|
|
|
|
|
```python
|
|
# Builder
|
|
class CourseBuilder(object):
|
|
def __init__(self, teacher):
|
|
self.teacher = teacher
|
|
|
|
def build_course(self):
|
|
self.teacher.provide_homework()
|
|
self.teacher.provide_exam()
|
|
return self.teacher.course
|
|
|
|
# Teacher
|
|
class Teacher(object):
|
|
def __init__(self, name=None):
|
|
self.name = name
|
|
self.course = Course()
|
|
|
|
def provide_homework(self):
|
|
raise NotImplementedError
|
|
|
|
def provide_exam(self):
|
|
raise NotImplementedError
|
|
|
|
|
|
class MathTeacher(Teacher):
|
|
def provide_homework(self):
|
|
self.course.homework = 'This is Math homework provided by {}.'.format(self.name)
|
|
|
|
def provide_exam(self):
|
|
self.course.exam = 'This is Math exam tested by {}.'.format(self.name)
|
|
|
|
|
|
class HistoryTeacher(Teacher):
|
|
def provide_homework(self):
|
|
self.course.homework = 'This is History homework provided by {}.'.format(self.name)
|
|
|
|
def provide_exam(self):
|
|
self.course.exam = 'This is History exam tested by {}.'.format(self.name)
|
|
|
|
|
|
# Target objects to be produced
|
|
class Course(object):
|
|
def __init__(self):
|
|
self.homework = None
|
|
self.exam = None
|
|
|
|
def __str__(self):
|
|
return 'Homework: {}\nExam: {}\n'.format(self.homework, self.exam)
|
|
|
|
|
|
math_course = CourseBuilder(MathTeacher('Harry')).build_course()
|
|
print(math_course)
|
|
>>> Homework: This is Math homework provided by Harry.
|
|
>>> Exam: This is Math exam tested by Harry.
|
|
|
|
history_course = CourseBuilder(HistoryTeacher('Potter')).build_course()
|
|
print(history_course)
|
|
>>> Homework: This is History homework provided by Potter.
|
|
>>> Exam: This is History exam tested by Potter.
|
|
```
|