python创建型设计模式学习——抽象工厂模式

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/huxiaotong_exp/article/details/53976224

python创建型设计模式学习

抽象工厂模式

抽象工厂模式用来创建复杂对象，这种对象由许多小对象组成，而这些小对象都属于某个特定的系列。例如GUI系统里面的“抽象控件工厂”

用字符串GUI的文本格式和svg格式的抽象工厂来说明

经典风格的抽象工厂模式

顶层调用

def main():
    ...
    txtDiagram = create_diagram(DiagramFactory())
    txtDiagram.save(textFilename)
    print("wrote", textFilename)

    svgDiagram = create_diagram(SvgDiagramFactory())
    svgDiagram.save(svgFilename)
    print("wrote", svgFilename)

中间调用

def create_diagram(factory):
    diagram = factory.make_diagram(30, 7)
    rectangle = factory.make_rectangle(4, 1, 22, 5, "yellow")
    text = factory.make_text(7, 3, "Abstract Factory")
    diagram.add(rectangle)
    diagram.add(text)
    return diagram

经典工厂类
存在的问题：
这两个工厂没有各自的状态，不需要创建工厂实例
两个工厂类的代码几乎一模一样，产生很多无谓的重复代码

class DiagramFactory:

    def make_diagram(self, width, height):
        return Diagram(width, height)


    def make_rectangle(self, x, y, width, height, fill="white",
            stroke="black"):
        return Rectangle(x, y, width, height, fill, stroke)


    def make_text(self, x, y, text, fontsize=12):
        return Text(x, y, text, fontsize)



class SvgDiagramFactory(DiagramFactory):

    def make_diagram(self, width, height):
        return SvgDiagram(width, height)


    def make_rectangle(self, x, y, width, height, fill="white",
            stroke="black"):
        return SvgRectangle(x, y, width, height, fill, stroke)


    def make_text(self, x, y, text, fontsize=12):
        return SvgText(x, y, text, fontsize)

经典模型类：
存在的问题：DiagramFactory、Diagram、Rectangle、Text都房主扩了顶级命名空间，导致取名时为了区别，增加前缀，使代码不够整洁。

BLANK = " "
CORNER = "+"
HORIZONTAL = "-"
VERTICAL = "|"


class Diagram:

    def __init__(self, width, height):
        self.width = width
        self.height = height
        self.diagram = _create_rectangle(self.width, self.height, BLANK)


    def add(self, component):
        for y, row in enumerate(component.rows):
            for x, char in enumerate(row):
                self.diagram[y + component.y][x + component.x] = char


    def save(self, filenameOrFile):
        file = None if isinstance(filenameOrFile, str) else filenameOrFile
        try:
            if file is None:
                file = open(filenameOrFile, "w", encoding="utf-8")
            for row in self.diagram:
                print("".join(row), file=file)
        finally:
            if isinstance(filenameOrFile, str) and file is not None:
                file.close()


def _create_rectangle(width, height, fill):
    rows = [[fill for _ in range(width)] for _ in range(height)]
    for x in range(1, width - 1):
        rows[0][x] = HORIZONTAL
        rows[height - 1][x] = HORIZONTAL
    for y in range(1, height - 1):
        rows[y][0] = VERTICAL
        rows[y][width - 1] = VERTICAL
    for y, x in ((0, 0), (0, width - 1), (height - 1, 0),
            (height - 1, width -1)):
        rows[y][x] = CORNER
    return rows


class Rectangle:

    def __init__(self, x, y, width, height, fill, stroke):
        self.x = x
        self.y = y
        self.rows = _create_rectangle(width, height,
                BLANK if fill == "white" else "%")


class Text:

    def __init__(self, x, y, text, fontsize):
        self.x = x
        self.y = y
        self.rows = [list(text)]


SVG_START = """<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN"
    "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
<svg xmlns="http://www.w3.org/2000/svg"
    xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve"
    width="{pxwidth}px" height="{pxheight}px">"""

SVG_END = "</svg>\n"

SVG_RECTANGLE = """<rect x="{x}" y="{y}" width="{width}" \
height="{height}" fill="{fill}" stroke="{stroke}"/>"""

SVG_TEXT = """<text x="{x}" y="{y}" text-anchor="left" \
font-family="sans-serif" font-size="{fontsize}">{text}</text>"""

SVG_SCALE = 20


class SvgDiagram:


    def __init__(self, width, height):
        pxwidth = width * SVG_SCALE
        pxheight = height * SVG_SCALE
        self.diagram = [SVG_START.format(**locals())]
        outline = SvgRectangle(0, 0, width, height, "lightgreen", "black")
        self.diagram.append(outline.svg)


    def add(self, component):
        self.diagram.append(component.svg)


    def save(self, filenameOrFile):
        file = None if isinstance(filenameOrFile, str) else filenameOrFile
        try:
            if file is None:
                file = open(filenameOrFile, "w", encoding="utf-8")
            file.write("\n".join(self.diagram))
            file.write("\n" + SVG_END)
        finally:
            if isinstance(filenameOrFile, str) and file is not None:
                file.close()


class SvgRectangle:

    def __init__(self, x, y, width, height, fill, stroke):
        x *= SVG_SCALE
        y *= SVG_SCALE
        width *= SVG_SCALE
        height *= SVG_SCALE
        self.svg = SVG_RECTANGLE.format(**locals())


class SvgText:

    def __init__(self, x, y, text, fontsize):
        x *= SVG_SCALE
        y *= SVG_SCALE
        fontsize *= SVG_SCALE // 10
        self.svg = SVG_TEXT.format(**locals())

python风格抽象工厂模式

改进：
将Diagram Text Rectangle等类以及相关常量嵌套到工厂类里面，用 xxxFactory.Text来引用。
用装饰器来修饰工厂类方法，使代码那不重复

class DiagramFactory:

    @classmethod
    def make_diagram(Class, width, height):
        return Class.Diagram(width, height)


    @classmethod
    def make_rectangle(Class, x, y, width, height, fill="white",
            stroke="black"):
        return Class.Rectangle(x, y, width, height, fill, stroke)

    @classmethod
    def make_text(Class, x, y, text, fontsize=12):
        return Class.Text(x, y, text, fontsize)


    BLANK = " "
    CORNER = "+"
    HORIZONTAL = "-"
    VERTICAL = "|"


    class Diagram:

        def __init__(self, width, height):
            self.width = width
            self.height = height
            self.diagram = DiagramFactory._create_rectangle(self.width,
                    self.height, DiagramFactory.BLANK)


        def add(self, component):
            for y, row in enumerate(component.rows):
                for x, char in enumerate(row):
                    self.diagram[y + component.y][x + component.x] = char


        def save(self, filenameOrFile):
            file = (None if isinstance(filenameOrFile, str) else
                    filenameOrFile)
            try:
                if file is None:
                    file = open(filenameOrFile, "w", encoding="utf-8")
                for row in self.diagram:
                    print("".join(row), file=file)
            finally:
                if isinstance(filenameOrFile, str) and file is not None:
                    file.close()


    class Rectangle:

        def __init__(self, x, y, width, height, fill, stroke):
            self.x = x
            self.y = y
            self.rows = DiagramFactory._create_rectangle(width, height,
                    DiagramFactory.BLANK if fill == "white" else "%")


    class Text:

        def __init__(self, x, y, text, fontsize):
            self.x = x
            self.y = y
            self.rows = [list(text)]


    def _create_rectangle(width, height, fill):
        rows = [[fill for _ in range(width)] for _ in range(height)]
        for x in range(1, width - 1):
            rows[0][x] = DiagramFactory.HORIZONTAL
            rows[height - 1][x] = DiagramFactory.HORIZONTAL
        for y in range(1, height - 1):
            rows[y][0] = DiagramFactory.VERTICAL
            rows[y][width - 1] = DiagramFactory.VERTICAL
        for y, x in ((0, 0), (0, width - 1), (height - 1, 0),
                (height - 1, width -1)):
            rows[y][x] = DiagramFactory.CORNER
        return rows


class SvgDiagramFactory(DiagramFactory):

    # The make_* class methods are inherited

    SVG_START = """<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN"
    "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
<svg xmlns="http://www.w3.org/2000/svg"
    xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve"
    width="{pxwidth}px" height="{pxheight}px">"""

    SVG_END = "</svg>\n"

    SVG_RECTANGLE = """<rect x="{x}" y="{y}" width="{width}" \
height="{height}" fill="{fill}" stroke="{stroke}"/>"""

    SVG_TEXT = """<text x="{x}" y="{y}" text-anchor="left" \
font-family="sans-serif" font-size="{fontsize}">{text}</text>"""

    SVG_SCALE = 20


    class Diagram:

        def __init__(self, width, height):
            pxwidth = width * SvgDiagramFactory.SVG_SCALE
            pxheight = height * SvgDiagramFactory.SVG_SCALE
            self.diagram = [SvgDiagramFactory.SVG_START.format(**locals())]
            outline = SvgDiagramFactory.Rectangle(0, 0, width, height,
                    "lightgreen", "black")
            self.diagram.append(outline.svg)


        def add(self, component):
            self.diagram.append(component.svg)


        def save(self, filenameOrFile):
            file = (None if isinstance(filenameOrFile, str) else
                    filenameOrFile)
            try:
                if file is None:
                    file = open(filenameOrFile, "w", encoding="utf-8")
                file.write("\n".join(self.diagram))
                file.write("\n" + SvgDiagramFactory.SVG_END)
            finally:
                if isinstance(filenameOrFile, str) and file is not None:
                    file.close()


    class Rectangle:

        def __init__(self, x, y, width, height, fill, stroke):
            x *= SvgDiagramFactory.SVG_SCALE
            y *= SvgDiagramFactory.SVG_SCALE
            width *= SvgDiagramFactory.SVG_SCALE
            height *= SvgDiagramFactory.SVG_SCALE
            self.svg = SvgDiagramFactory.SVG_RECTANGLE.format(**locals())


    class Text:

        def __init__(self, x, y, text, fontsize):
            x *= SvgDiagramFactory.SVG_SCALE
            y *= SvgDiagramFactory.SVG_SCALE
            fontsize *= SvgDiagramFactory.SVG_SCALE // 10
            self.svg = SvgDiagramFactory.SVG_TEXT.format(**locals())

补充知识点：

locals()函数：
http://www.cnblogs.com/nerrissa/articles/4699483.html

str.format(**locals()):
https://zhidao.baidu.com/question/344727191.html
format()只会取local()中用得的关键字参数

enumerate()函数的用法：
http://blog.csdn.net/churximi/article/details/51648388

类方法 静态方法 实例方法 普通函数 区别与关系：
http://www.cnblogs.com/funfunny/p/5892212.html