使用默认值初始化记录

Question

使用默认值初始化记录的常见做法是什么,除非明确指定这些记录？

为了说明我的问题,请使用以下python代码:

class Encoder:
    def __init__ (self, minLength = 1, maxLength = 258, maxDistance = 32768):
        self.__minLength = minLength
        self.__maxLength = maxLength
        self.__maxDistance = maxDistance
        self.__window = []
        self.__buffer = []

现在我试图在erlang中做同样的事情,即创建一个具有可覆盖默认值的记录.到目前为止我的解决方案如下:

-record (encoder, {minLength, maxLength, maxDistance, window = [], buffer = [] } ).

init (Options) ->
    case lists:keyfind (minLength, 1, Options) of
        false -> MinLength = 3;
        {minLength, MinLength} -> pass
    end,
    case lists:keyfind (maxLength, 1, Options) of
        false -> MaxLength = 258;
        {maxLength, MaxLength} -> pass
    end,
    case lists:keyfind (maxDistance, 1, Options) of
        false -> MaxDistance = 32768;
        {maxDistance, MaxDistance} -> pass
    end,
    #encoder {minLength = MinLength,
        maxLength = MaxLength,
        maxDistance = MaxDistance}.

这很笨拙.

我的问题是:

• 是否有一些语言结构或语法糖可以节省我所有这些代码？
• 实现这一目标的常见做法是什么？
• 使用的常用做法代替了我pass明显从python中偷走的原子？

Answer 1

您可以像这样使用proplists模块:

-record (encoder, {minLength, maxLength, maxDistance, window = [], buffer = [] } ).

init (Options) ->
    #encoder {minLength = proplists:get_value(minLength, Options, 1),
        maxLength = proplists:get_value(maxLength, Options, 256),
        maxDistance = proplists:get_value(maxDistance, Options, 32768)}.