如何使用值构造函数在 PureScript 中创建记录

Question

我正在尝试基于数据数组创建记录，函数如下所示：

type Address = {
  street :: String,
  city :: String,
  state :: String
}

convertToAddress :: Array String -> Maybe Address
convertToAddress [street, city, state] = Just (Address { street: street, city: city, state: state })
convertToAddress _ = Nothing

在这里，我尝试使用 Address 值构造函数创建一个 Address 类型的 Record，但它在编译时抛出错误：

Unknown data constructor Address

Answer 1

type 只定义了一个类型别名，所以 Address 和

{
  street :: String,
  city :: String,
  state :: String
}

其实是同一种类型。如果要生成构造函数，则必须使用 newtype:

newtype Address = Address {
  street :: String,
  city :: String,
  state :: String
}

或者，您可以去掉代码中的构造函数，只使用记录类型：

convertToAddress :: Array String -> Maybe Address
convertToAddress [street, city, state] = Just { street: street, city: city, state: state }
convertToAddress _ = Nothing

如何使用值构造函数在 PureScript 中创建记录

How to use Value constructors to create records in PureScript

record

adt

purescript