Downloading a JSON file as an Unauthenticated user AWS/S3/Cognito - swift

Question

I am trying to download a JSON file which is in my bucket in my S3 on my AWS account. I created an Unauthenticated cognito pool and copied this into my app delegate from the sample code:
let credentialsProvider = AWSCognitoCredentialsProvider(regionType:.USWest2,
identityPoolId:"us-west-2:59a31a8f-ee6a-45fe-adaa-fa3eff871c80")
let configuration = AWSServiceConfiguration(region:.USWest2, credentialsProvider:credentialsProvider)
AWSServiceManager.default().defaultServiceConfiguration = configuration
In my view controller I have this code:
let transferManager = AWSS3TransferManager.default()
let downloadingFileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("db_storage/costdb_latest.json ")
if let downloadRequest = AWSS3TransferManagerDownloadRequest(){
downloadRequest.bucket = "coast-s3-bucket"
downloadRequest.key = "db_storage/costdb_latest.json "
downloadRequest.downloadingFileURL = downloadingFileURL
transferManager.download(downloadRequest).continueWith(executor: AWSExecutor.default(), block: { (task: AWSTask<AnyObject>) -> Any? in
if( task.error != nil){
print(task.error!.localizedDescription)
return nil
}
print(task.result!)
if let data = NSData(contentsOf: downloadingFileURL){
DispatchQueue.main.async(execute: { () -> Void in
print(data)
})
}
return nil
})
}
Both the bucket and the pool are in the same region. USWest2 (Oregon). My bucket is public, and I've added AmazonS3FullAccess and AmazonS3ReadOnlyAccess to my policies. And I'm getting this error:
The operation couldn’t be completed. (com.amazonaws.AWSS3ErrorDomain error 4.)

Answer 1

Its not an authentication/authorization error (I think). From the looks of it, there is some issue with the configuration (region,endpoint etc.). Generally, these errors contain a full description of what's wrong. Try logging the full error message.
Also, see this example app for S3 TransferManager. Use your S3 & Cognito details. If this works, there is some code issue and you can find out by comparing both of these. If this does not work, then this could be a service issue.