Month: May 2020

When you write your own Resolvers for AWS AppSync, you are given a $context object that contains a lot of helpful things. In my case I needed to grab a unique ID associated with the user from the Cognito User Pool I set up. But the $ctx.identity.cognitoIdentityId just wasn’t there. I needed to find out what I could use there.

Normally my response template looks like this:

#if($ctx.error)
    $utils.error($ctx.error.message, $ctx.error.type)
#end

$utils.toJson($utils.rds.toJsonObject($ctx.result)[1][0])

In my case it was telling me that a value was required. So I changed the template to spit out the whole context object instead of just the message:

#if($ctx.error)
    $utils.error($utils.toJson($ctx), $ctx.error.type)
#end

Then I went to Queries and ran it again, this time getting the whole context spat out as the “error”. A trip through a JSON unescape tool and formatting with the JSON Viewer Notepad++ plugin gave me a complete picture of what’s available.

Turns out I need to use sub or username, and the cognitoIdentityId field is nowhere to be found.