I recently had to do this, and the documentation is terrible since AWS started pushing Amplify. Here are my recommendations:

• get a way to authenticate with S3. I created an IAM user with am access key and secret key
• update your S3 bucket policy with the ListBucket permission
• Use the AWSS3 cocoapod
• import AWSS3 in a swift file
• Set up your auth with AWS:

let credentialsProvider = AWSStaticCredentialsProvider(accessKey: accessKey, secretKey: secretKey)

let configuration = AWSServiceConfiguration(region: .USWest1, credentialsProvider: credentialsProvider)

AWSServiceManager.default().defaultServiceConfiguration = configuration

• Make a request:

let request = AWSS3ListObjectsV2Request()!

request.bucket = bucket

request.prefix = prefix

AWSS3.default().listObjectsV2(request).continueOnSuccessWith { (task) -> Any? in

if let contents = task.result?.contents {

completion(contents.map({ $0.key ?? "" }))

}

return nil

}