外观模式相对简单 这里只说明概念，和网上的code
外观模式（Facade Pattern）
意图：为子系统中的一组接口提供一个一致的界面，外观模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。
主要解决：降低访问复杂系统的内部子系统时的复杂度，简化客户端与之的接口。
何时使用：
1、客户端不需要知道系统内部的复杂联系，整个系统只需提供一个"接待员"即可。
2、定义系统的入口。
如何解决：客户端不与系统耦合，外观类与系统耦合。
dart代码
main(List<String> args) {
ShapeMaker shapeMaker = new ShapeMaker();
shapeMaker.drawCircle();
shapeMaker.drawRectangle();
shapeMaker.drawSquare();
}
//////////////////////////////////////////////////////////////////
///
/// 创建一个接口
///
abstract class Shape {
void draw();
}
///
/// 创建实现接口的实体类
///
class Rectangle implements Shape {
@override
void draw() {
print("Rectangle::draw()");
}
}
class Square implements Shape {
@override
void draw() {
print("Square::draw()");
}
}
class Circle implements Shape {
@override
void draw() {
print("Circle::draw()");
}
}
///
/// 创建一个外观类
///
class ShapeMaker {
Shape circle;
Shape rectangle;
Shape square;
ShapeMaker() {
circle = Circle();
rectangle = Rectangle();
square = Square();
}
void drawCircle() {
circle.draw();
}
void drawRectangle() {
rectangle.draw();
}
void drawSquare() {
square.draw();
}
}
python 代码
from abc import ABCMeta, abstractmethod
from enum import Enum
State = Enum('State', 'new running sleeping restart zombie')
class Server(metaclass=ABCMeta):
""" 抽象基类 """
@abstractmethod
def __init__(self):
pass
def __str__(self):
return self.name
@abstractmethod
def boot(self):
pass
@abstractmethod
def kill(self, restart=True):
pass
class FileServer(Server):
def __init__(self):
'''actions required for initializing the file server'''
self.name = 'FileServer'
self.state = State.new
def boot(self):
print('booting the {}'.format(self))
'''actions required for booting the file server'''
self.state = State.running
def kill(self, restart=True):
print('Killing {}'.format(self))
'''actions required for killing the file server'''
self.state = State.restart if restart else State.zombie
def create_file(self, user, name, permissions):
'''check validity of permissions, user rights, etc.'''
print("trying to create the file '{}' for user '{}' with permissions {}".format(name, user, permissions))
class ProcessServer(Server):
def __init__(self):
'''actions required for initializing the process server'''
self.name = 'ProcessServer'
self.state = State.new
def boot(self):
print('booting the {}'.format(self))
'''actions required for booting the process server'''
self.state = State.running
def kill(self, restart=True):
print('Killing {}'.format(self))
'''actions required for killing the process server'''
self.state = State.restart if restart else State.zombie
def create_process(self, user, name):
'''check user rights, generate PID, etc.'''
print("trying to create the process '{}' for user '{}'".format(name, user))
class OperatingSystem:
''' 实现外观模式，外部使用的代码不必知道 FileServer 和 ProcessServer的
内部机制，只需要通过 OperatingSystem类调用'''
def __init__(self):
self.fs = FileServer()
self.ps = ProcessServer()
def start(self):
""" 被客户端代码使用 """
[i.boot() for i in (self.fs, self.ps)]
def create_file(self, user, name, permissions):
return self.fs.create_file(user, name, permissions)
def create_process(self, user, name):
return self.ps.create_process(user, name)
def main():
os = OperatingSystem()
os.start()
os.create_file('foo', 'hello', '-rw-r-r')
os.create_process('bar', 'ls /tmp')
main()
