graphql server, resolver depended on another resolver

Question

assume I have schema like this

type Result{ fieldA: TypeA, fieldB: TypeB, # other fileds ... }

fieldB is computed based on fieldA like:

function getData(){...}
function transformData(){...}
resolverA:()=>getData()
resolverB:()=>transformData(getData())

queries could ask for either/both or non of field A/B

assume both getData() and transformData() are expensive operations,

how do I write the resolvers so that :

1) resolverB use the resolved data from resolverA

2) getData only gets called once when both AB fields are in the query

3) None of getData/transformData gets called when only asking for other fields

Ionut Achim · Accepted Answer · 2017-11-29 20:26:58Z

2

I would probably just memoize getData and be done with it. You can use dataloader for that or write your own simple closure that resets it's data on the next tick:

const getData = (function () {
  let cache
  return function () {
    if (cache) return cache
    cache = // do heavy stuff

    process.nextTick(() => {
      cache = null
    })
    return cache
  }
})()

edited Nov 29, 2017 at 20:26

answered Nov 29, 2017 at 20:09

Ionut Achim

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1 Comment

Oleg Vazhnev Over a year ago

If we use GraphQLRootContext as cache it will soon contain everything and become dirty. If we don't use GraphQLRootContext as cache, then what should we use?

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