Platform

Swift 4, iOS 13, Xcode 11. Using Amplify, GraphQL, Cognito

Problem

I want to trigger an AWS lambda function called onCall. It has been written and is just a simple blank function. On the client side I am following [1] and have:

    let lambdaInvoker = AWSLambdaInvoker.default()

    let jsonObject: [String: Any] = [
        "key1" : "value1",
         "key2" : 2 ,
         "key3" : [1, 2],
         "isError" : false
    ]

    lambdaInvoker.invokeFunction("onCall", jsonObject: jsonObject)
        .continueWith(block: {(task:AWSTask<AnyObject>) -> Any? in
        if( task.error != nil) {
            print("Error: \(task.error!)")
            return nil
        }

        print(">> lambda \(task)")

        // Handle response in task.result
        return nil
    })

But I get a permission denied error:

Error: Error Domain=com.amazonaws.AWSLambdaErrorDomain Code=0 "AccessDeniedException" UserInfo={StatusCode=403, responseStatusCode=403, responseHeaders={type = immutable dict, count = 5, entries => 2 : x-amzn-requestid = {contents = "83047425-06c6-4193-b5c6-ac8461d84aa0"} 3 : Content-Length = 243 4 : Content-Type = {contents = "application/json"} 5 : x-amzn-errortype = {contents = "AccessDeniedException"} 6 : Date = {contents = "Thu, 07 May 2020 02:18:00 GMT"} } , Message=User: arn:aws:sts::870560247484:assumed-role/amplify-alpha-alphaenv-123654-authRole/CognitoIdentityCredentials is not authorized to perform: lambda:InvokeFunction on resource: arn:aws:lambda:us-east-1:870560247484:function:onCall, responseDataSize=243, NSLocalizedFailureReason=AccessDeniedException}

I have this line in my awsconfiguration.json file

"LambdaInvoker" : {
  "Default" : {
       "Region": "us-east-1"
  }
}

Now in the docs it says I should use Amplify API, but I cannot find any amplify API for triggering lambda, and the doc is very sparse beyond basic use cases.

Acceptable solutions

1. Making the lambdaInvoker work as is, regardless of the statement about Amplify.

2. Point me or provide code example for calling lamdas in Amplify API

[1] https://docs.aws.amazon.com/aws-mobile/latest/developerguide/how-to-ios-lambda.html