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