代码之家 › 专栏 › 技术社区 › Franz Wong

当值为正时设置属性

sanctuary ramda.js

0

Franz Wong · 技术社区 · 7 年前

我希望在值为Just时设置对象的属性,而不是在值为Nothing时设置属性。但是,如果值为Nothing,则返回的对象将变为Nothing。

let person = {name: 'Franz'}
const address = getAddress(response) // getAddress returns Maybe

// person will be Nothing if address is Nothing 
person = S.map(R.assoc('address', R.__, person))(address)

1 回复 | 直到 7 年前

1

davidchambers 7 年前

看来你的 Person

Person = { name :: String, (address :: Address)? }

如果可能的话,我建议避免 null , undefined

//    person :: Person
const person = {name: 'Franz', address: S.Nothing};

//    address :: Maybe Address
const address = getAddress (response);

//    person$ :: Person
const person$ = R.assoc ('address') (address) (person);

address 字段在本例中,您可以使用 S.maybe :

//    person :: Person
const person = {name: 'Franz'}

//    address :: Maybe Address
const address = getAddress (response);

//    person$ :: Person
const person$ = S.maybe (person)
                        (address => R.assoc ('address') (address) (person))
                        (address);

结果要么是 {name: 'Franz'} {name: 'Franz', address: 'Frankfurter Allee 42'} . 不过,正如我所提到的, {name: 'Franz', address: S.Nothing} {name: 'Franz', address: S.Just ('Frankfurter Allee 42')} 是这些人的更好的代表。