How to invoke an AWS Lambda function in Swift - swift

Question

I can't find any documentation or examples on how to invoke a Lambda function in Swift but I've tried to extrapolate from the documentation using Objective-C and I'm still getting errors:
"Error in myFunction: ValidationException: Supplied AttributeValue is empty, must contain exactly one of the supported datatypes"
It appears that I'm not passing in the parameters to the function correctly when I invoke the lambda function from swift because the script tries to write to DynamoDB but one of the parameters is empty (this lambda script works when I invoke it in javascript/node).
let lambda = AWSLambda.defaultLambda()
let request = AWSLambdaInvocationRequest()
var context = [String: String]()
let jsonString = "{\"email\":\"example#example.com\",\"name\":\"example\"}"
let jsonData = jsonString.dataUsingEncoding(NSUTF8StringEncoding)
request.clientContext = jsonData?.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)
request.functionName = "myFunction"
lambda.invoke(request).continueWithBlock( {
(currentTask: AWSTask!) -> AWSTask in
if (currentTask.error != nil) {
// failed to execute.
print("Error executing: ", currentTask.error)
task.setError(currentTask.error)
} else {
print("token: ", currentTask.result)
task.setResult(currentTask.result)
}
return currentTask
})

Answer 1

You need to set the payload parameter to a map containing the data you want to pass.
let invocationRequest = AWSLambdaInvokerInvocationRequest()
invocationRequest.functionName = "myFunction"
invocationRequest.invocationType = AWSLambdaInvocationType.RequestResponse
invocationRequest.payload = ["email" : "example#example.com", "name" : "example"]
let lambdaInvoker = AWSLambdaInvoker.defaultLambdaInvoker()
let task = lambdaInvoker.invoke(invocationRequest).continueWithSuccessBlock() { (task) -> AWSTask! in
print("response: ", task.result)
}

Answer 2

Ryan Fitzgerald's answer gives me multiple compile-time errors, but I've had success with this version:
First, I have an initialization function with access credentials. Note that this is not the recommended secure access method for production code, but it is fine for testing and other purposes. It also assumes you have a Constants.swift file where you define the listed constants:
func initializeLambda() {
let credentialsProvider = AWSStaticCredentialsProvider.init(accessKey:Constants.AWS_ACCESS_KEY, secretKey: Constants.AWS_SECRET_KEY)
let defaultServiceConfiguration = AWSServiceConfiguration(region: Constants.AWS_REGION, credentialsProvider: credentialsProvider)
AWSServiceManager.defaultServiceManager().defaultServiceConfiguration = defaultServiceConfiguration
}
For the remainder we can provide a version similar to the previous version. I removed the 'let task' because 'task' is not used in his example. Additionally, I've included the logical outline of some JSON parsing that you are likely to be doing inside the invoke task. Finally, I've changed to a continueWithBlock(). If you use a continueWithSuccessBlock() you will not enter this block when Amazon Lambda reaches its timeout window or if something else goes wrong with the request and typically you do want these situations to be handled here.
self.initializeLambda() //Call our previously written initialization function
let invocationRequest = AWSLambdaInvokerInvocationRequest()
invocationRequest.functionName = "functionName"
invocationRequest.invocationType = AWSLambdaInvocationType.RequestResponse
invocationRequest.payload = ["key1" : "value1", "key2" : "value2"]
let lambdaInvoker = AWSLambdaInvoker.defaultLambdaInvoker()
lambdaInvoker.invoke(invocationRequest).continueWithBlock() { (task: AWSTask) -> AWSTask in
print("response: ", task.result)
//In here you'll likely be parsing a JSON payload
if let payload: AnyObject = task.result?.payload {
if let error: AnyObject = payload.objectForKey("error") {
//If there is an error key in the JSON dictionary...
} else {
//If the JSON dictionary has no error key...
}
return task;
}
}
Tested and verified as functional on Swift 2.2 in Xcode 7.3.

Answer 3

The answers from both the Ryan's were great and useful and I just want to add a couple of additional thoughts.
In most cases, before you can invoke a Lambda, you might need to authenticate, so the errors you get might not necessarily be because of your Lambda calls but due to failing authentication. With AWS, however, there are several different ways to authenticate and this will change based on the credentials you have.
Ryan Davis shows you one way where your backend team has set up an AWS Access Key and an AWS Secret Key.
In my case, I had to authenticate using AWS Cognito Identity Pools and there are also User Pool authentication so you need to figure out what credentials your team has given you and read the appropriate authentication documentation.
Since I needed to use using AWS Cognito Identity Pools, all I had was the region and the identity pool id so in Swift 5 authentication for AWS Cognito Identity Pools
let credentialsProvider = AWSCognitoCredentialsProvider(regionType: Constants.AWS_REGION,
identityPoolId: Constants.AWS_REGION.AWS_IDENTITY_POOL_ID)
let serviceConfiguration = AWSServiceConfiguration(region: Constants.AWS_REGION,
credentialsProvider: credentialsProvider)
AWSServiceManager.default().defaultServiceConfiguration = serviceConfiguration
And then the Lambda invocation more or less stays the same but just with slightly updated Swift 5 syntax:
if let invocationRequest = AWSLambdaInvokerInvocationRequest() {
invocationRequest.functionName = "function_name"
invocationRequest.invocationType = AWSLambdaInvocationType.requestResponse
invocationRequest.payload = ["key_1": "value_1"]
let lambdaInvoker = AWSLambdaInvoker.default()
lambdaInvoker.invoke(invocationRequest) { (awsLambdaInvokerInvocationResponse, error) in
guard let payload = awsLambdaInvokerInvocationResponse?.payload as? [String: String] else {
// Handle error here
return
}
if let userId = payload["message"] {
print("USR Id: \(userId)")
}
}
}
You will need to adjust your handling based on the structure of your payload returned to you by the Lambda, in my case it was:
{
"message": "user-id-8868-8475-8757"
}
Finally, remember to import the required libraries for your use case, for my above case I needed:
import AWSCore
import AWSLambda