I have a method which requires multiple arguments, and I am trying to set up a ramda pipe to handle it.

Here's an example:

const R = require('ramda');
const input = [
  { data: { number: 'v01', attached: [ 't01' ] } },
  { data: { number: 'v02', attached: [ 't02' ] } },
  { data: { number: 'v03', attached: [ 't03' ] } },
]

const method = R.curry((number, array) => {
  return R.pipe(
    R.pluck('data'),
    R.find(x => x.number === number),
    R.prop('attached'),
    R.head
  )(array)
})

method('v02', input)

Is there a cleaner way of doing this, especially the x => x.number === number part of filter and having to call (array) at the end of the pipe?

Here's a link to the code above loaded into the ramda repl.

I have a method which requires multiple arguments, and I am trying to set up a ramda pipe to handle it.

Here's an example:

const R = require('ramda');
const input = [
  { data: { number: 'v01', attached: [ 't01' ] } },
  { data: { number: 'v02', attached: [ 't02' ] } },
  { data: { number: 'v03', attached: [ 't03' ] } },
]

const method = R.curry((number, array) => {
  return R.pipe(
    R.pluck('data'),
    R.find(x => x.number === number),
    R.prop('attached'),
    R.head
  )(array)
})

method('v02', input)

Is there a cleaner way of doing this, especially the x => x.number === number part of filter and having to call (array) at the end of the pipe?

Here's a link to the code above loaded into the ramda repl.

• javascript
• ramda.js

2 Answers 2

One way this could possibly be rewritten:

const method = R.curry((number, array) => R.pipe(
  R.find(R.pathEq(['data', 'number'], number)),
  R.path(['data', 'attached', 0])
)(array))

Here we've replaced the use of R.pluck and the anonymous function given to R.find with R.pathEq given as the predicate to R.find instead. Once found, the value can be retrieved by walking down the properties of the object with R.path.

It is possible to rewrite this in a point-free manner using R.useWith, though I feel readability gets lost in the process.

const method = R.useWith(
  R.pipe(R.find, R.path(['data', 'attached', 0])),
  [R.pathEq(['data', 'number']), R.identity]
)

I think readability could be improved using pluck and prop instead of path. Like this:

const method = R.useWith(
  R.pipe(R.find, R.prop('attached')),
  [R.propEq('number'), R.pluck('data')]
);

And of course, it's better to use a good name for the function. Like getAttachedValueByNumber.