使用 Ramda 根据条件过滤对象

Question

我想使用 Ramda 过滤掉以下数据。期望的结果是显示属性 usage === 'Defining'.

const data = 
[{
  "attributes":
  [
    {"usage": "Descriptive"},
    {"usage": "Defining"}
  ]
}]

到目前为止，这就是我所做的，它没有过滤掉数据并返回整个对象。

R.filter(
 R.compose(
     R.any(R.propEq('usage', 'Defining')),
     R.prop('attributes')
  )
)(data)

以下是我想要达到的预期结果：

[{
  "attributes":
  [
    {"usage": "Defining"}
  ]
}]

Answer 1

您正在尝试在此处同时执行地图和过滤器，因此值得为每个单独的函数，然后将它们组合在一起以获得您想要的：

const data = 
[{
  "attributes":
  [
    {"usage": "Descriptive"},
    {"usage": "Defining"}
  ]
},
{
  "attributes":
  [
    {"usage": "Descriptive"},
    {"usage": "Definingx"}
  ]
}]

const removeObjectsWithoutDefining = filter(
  compose(any(equals('Defining')), map(prop('usage')), prop('attributes'))
);

const adjustProp = curry((f, k, o) => ({
  ...o,
  [k]: f(o[k]),
}));

const mapAttributesToRemoveNonDefining = map(
    adjustProp(
      filter(propEq('usage', 'Defining')),
      'attributes',
    ),
)

const f = compose(mapAttributesToRemoveNonDefining, removeObjectsWithoutDefining);

f(data);

Ramda repl link.

Answer 2

如果我理解正确你想要做什么，那么 where 在你想要基于属性进行过滤时非常有用。但是您想将它与 map 结合起来。虽然 Ramda 不提供 filterMap，但编写我们自己的非常容易。我们创建一个接受过滤函数和映射函数的函数，以及 returns 一个接受数组并仅映射通过过滤器的结果的函数。以这种方式分解问题，我们可以这样写：

const filterMap = (f, m) => (xs) => 
  chain ((x) => f (x) ? [m (x)] : [], xs)

const definingProps = filterMap (
  where ({attributes: any (propEq ('usage', 'Defining'))}),
  over (lensProp('attributes'), filter (propEq ('usage', 'Defining')))
)

const data = [
  {id: 1, attributes: [{usage: "Descriptive"}, {usage: "Defining"}]},
  {id: 2, attributes: [{usage: "Descriptive"}, {usage: "Something Else"}]},
  {id: 3, attributes: [{usage: "Defining"}, {usage: "Filtering"}]}
]

console .log (definingProps (data))

.as-console-wrapper {min-height: 100% !important; top: 0}

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.27.0/ramda.js"></script>
<script> const {curry, chain, where, any, propEq, over, lensProp, filter} = R </script>

显然，将 propEq ('usage', 'Defining') 提取到独立函数中是有道理的；留作 reader.

的练习

使用 Ramda 根据条件过滤对象

Filtering objects based on conditions using Ramda

javascript

typescript

reactjs

ramda.js

react-native