haskellaeson

Data.Aeson import Key

I have the below code for parsing Int from an object. But unable to find the correct import for Key.

parseInt :: Object -> Key -> Parser Int
parseInt v field =
  asum
    [ v .: field,
      do
        s <- v .: field
        case readMaybe s :: Maybe Int of
          Nothing -> fail "not a number"
          Just x -> return x
    ]

I have tried

import Data.Aeson

and

import Data.Aeson.Types

But get the error

    Not in scope: type constructor or class ‘Key’
    A data constructor of that name is in scope; did you mean DataKinds?

What should be the correct import for Key in my function?

Solution

  • It looks like you're writing code targeting aeson 2.x, but that you have aeson 1.x installed. Either upgrade (recommended), or use Text in place of Key there.