66ws

In some cases we will have lots of args to initialize a class, this suppose to be:

• initialization with parts of args
• easily extend
• method chaining

class People:
  def __init__( self, Id: int, Name: str, aChar: str = 'a'):
    self.Id: int = Id
    self.Name: str = Name
    self.aChar: str = aChar
        ......

I suppose that it is a easiest example. But it has a little trouble. When we use a lots of args, it will be a terrible args' list. In next stage, try to solve "easily extend" and "long args' list".

class People:
  def __init__( self,Id: int, Name: str, **kw):
    self.Id: int = Id
    self.Name: str = Name
    self.aChar: str = kw.get("aChar","a")
    self.aIntArray: List[int] = kw.get("aIntArray",[1,2,3,4,5])
        ......

But it cannot verify that the type is correct (or value). Of course, you can do that like self.aChar: str = kw.get("aChar","a") if type(kw.get("aChar","a")) == "int" else .... But it not as expected. Go on.

class People:
  class Builder:
    def __init__( self, Id:int, Name: str):
      self.Id: int = Id
      self.Name: str = Name
      self.aChar: str = "a"
      self.aIntArray: List[int] = [1,2,3,4,5]
    def setAChar(self,x):
      if len(x) == 1: # verify the value
        self.aChar = x
      else:
        pass # something here
    def setAIntArray(self,x):
      Ints = [i==int(i) for i in x]
      if sum(Ints) != len(x):
        pass # something here 
      self.aIntArray = x
    def build(self):
      return People(self)
  def __init__( self,b: Builder):
    self.Id: int = b.Id
    self.Name: str = b.Name
    self.aChar: str = b.aChar
    self.aIntArray: List[int] = b.aIntArray

It is a good idea to use a builder class to build a class. But it use like-

p = People.build(1,"A")
p.setAChar("A")
p.setAIntArray([3,2,1])
 ...

I suppose that it could be simply.

  ...
  class Builder:
    def __init__( self, Id:int, Name: str):
      self.Id: int = Id
      self.Name: str = Name
      self.aChar: str = "a"
      self.aIntArray: List[int] = [1,2,3,4,5]
    def setAChar(self,x):
      if len(x) == 1: # verify the value
        self.aChar = x
      else:
        pass # something here
      return self
    def setAIntArray(self,x):
      Ints = [i==int(i) for i in x]
      if sum(Ints) != len(x):
        pass # something here 
      self.aIntArray = x
      return self
    def build(self):
      return People(self)
  ...

Now, it could use like-

p1 = People.build(1,"A").setAChar("A").setAIntArray([3,2,1]).build()
p2 = People.build(1,"B").setAChar("C").build()
 ...

We could merge it.

class People:
  class Builder:
    def __init__( self, Id:int, Name: str):
      self.Id: int = Id
      self.Name: str = Name
      self.aChar: str = "a"
      self.aIntArray: List[int] = [1,2,3,4,5]
    def setAChar(self,x):
      if len(x) == 1: # verify the value
        self.aChar = x
      else:
        pass # something here
      return self
    def setAIntArray(self,x):
      Ints = [i==int(i) for i in x]
      if sum(Ints) != len(x):
        pass # something here 
      self.aIntArray = x
      return self
    def build(self):
      return People(self)
  def __init__( self,b: Builder):
    self.Id: int = b.Id
    self.Name: str = b.Name
    self.aChar: str = b.aChar
    self.aIntArray: List[int] = b.aIntArray

END.