Styjun

I have a working REST API based on this API Gateway tutorial. I'm able to successfully invoke it via the test functionality of the AWS Console; and I'm able to successfully invoke it via my simple iOS Swift 4.2 Xcode application using the iPhone XR simulator.

I know it's working via a real, live external call because I can see the Cloudwatch logs which always register a 200 response and is sending the results back to the Client.

My problem is really in understanding the Swift code, and I'm hoping that a Swift expert can help me understand how to unpack result in the code below.

Here's my code in ViewController.swift for invoking the REST API and attempting to print result to the console:

@IBAction func userInvokeApi(_ sender: UIButton) 
 print("You clicked invoke api...")
 let client = SVTLambdaGateClient.default()
 client.calcGet(operand2: "3", _operator: "+", operand1: "5").continueWith (task: AWSTask?) -> AnyObject? in
 if let error = task?.error 
 print("Error occurred: (error)")
 return nil
 

 if let result = task?.result 
 // Do something with result
 print("The result is... (result)")
 

 return nil
 

As pointed out in the comments below, I'm getting the following result because it's printing out the address of the object:

You clicked invoke api...
The result is... <AmplifyRestApiTest.Empty: 0x600002020770> 

(where AmplifyRestApiTest is the name of my Xcode project.)

UPDATE When I set a breakpoint on the print statement, this is what I see in the Debug pane:

UPDATE 2
When I type task?.result there are two viable properties as per this answer from the Amplify team: error and result. So, since my API responds successfully I am assuming I just don't know how to view result.

Can someone help me understand what steps I must take to access members of this class object?

Here is the corresponding method in the API Gateway-generated iOS Swift SDK code:

/*
 @param operand2 
 @param _operator 
 @param operand1 

 return type: Empty
 */
public func calcGet(operand2: String, _operator: String, operand1: String) -> AWSTask<Empty> 
 let headerParameters = [
 "Content-Type": "application/json",
 "Accept": "application/json",

 ]

 var queryParameters:[String:Any] = [:]
 queryParameters["operand2"] = operand2
 queryParameters["operator"] = _operator
 queryParameters["operand1"] = operand1

 let pathParameters:[String:Any] = [:]

 return self.invokeHTTPRequest("GET", urlString: "/calc", pathParameters: pathParameters, queryParameters: queryParameters, headerParameters: headerParameters, body: nil, responseClass: Empty.self) as! AWSTask<Empty>

I'm fairly certain this return type of Empty refers to the Empty model defined for the REST API as shown in the screenshot below. I think it's "empty" because the API doesn't alter the response from the Lambda function back to the Client. So, it's all pass-through. Indeed, the tutorial explains that the other models -- Output and Result -- are not used because it "relies on the passthrough behavior and does not use this model."

Any thoughts?