使用构建器模式，我得到了attributeError：＆＃x27; noneType＆＃x27;对象没有属性属于构建器类功能

Question

我尝试实例我使用构建器模式进行的类

class Cat:
    def __init__(self,height,weight, color):
        self.height = height
        self.weight = weight
        self.color = color
    def print(self):
       print("%d %d %s" %(self.height,self.weight,self.color))
class CatBuilder:
    def __init__(self):
        self.weight = None
        self.height = None   
        self.color = None 
    def setWeight(self,weight):
        self.weight = weight
    def setHeight(self,height):
        self.height = height
    def setColor(self,color):
        self.color = color
    def build(self):
        cat = Cat(self.height,self.weight,self.color)
        return cat

，然后我使用以下代码运行cat1.print（）

#error version
cat1 = CatBuilder().setColor("red").setHeight(190).setWeight(80)
cat1.print()
#correct version
cat_builder = CatBuilder()
cat_builder.setColor("red")
cat_builder.setHeight(180)
cat_builder.setWeight(50)
cat2 = cat_builder.build()
cat2.print()

我认为这两个代码都是正确的，但是#Error版本不起作用。 我该如何修复？

Answer 1

我得到了答案！
我必须附加返回self代码如下：

class Cat:
    def __init__(self,height,weight, color):
        self.height = height
        self.weight = weight
        self.color = color
    def print(self):
       print("%d %d %s" %(self.height,self.weight,self.color))

class CatBuilder:
    def __init__(self):
        self.weight = None
        self.height = None   
        self.color = None 
    def setWeight(self,weight):
        self.weight = weight
        return self
    def setHeight(self,height):
        self.height = height
        return self
    def setColor(self,color):
        self.color = color
        return self
    def build(self):
        cat = Cat(self.height,self.weight,self.color)
        return cat