Styjun

I've followed two API Gateway tutorials for two different REST APIs that call AWS Lambda. Here's the link to the Calc API, which is the subject of this post.

In each case, test invocations via the AWS Console work perfectly. But when I generate the iOS Swift SDK from the deployed stage 'SDK Generation' tab, unzip and import into my Xcode project, the defaultClient member is missing in <API-Name>Client.swift.

The README.md file in each case says it should be there:

# Use the SDK in your project

1. Grab the `defaultClient` from your code

 let client = <API-Name>Client.defaultClient()

1. You can now call your method using the client SDK

But there is NO defaultClient in <API-Name>Client.swift.

UPDATE
There is no defaultClient, but there is a default (with backticks around it because default is a reserved word in Swift). So I substituted that in the REST API invocation... and it worked! I have no idea why... I don't know what the backticks mean in Swift... and if someone can explain this to me, great. But I verified via API Gateway that the API was called successfully; and I verified via Cloudwatch that the Lambda function returns the correct value.

Here is my code that invokes the API:

@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
 

However, I don't understand the data structure returned at the Client yet. This is what I get:

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

Here are the full contents of the generated <API-Name>Client.swift file (with some comments removed). I'm thinking it's possible that the README is no longer in sync with the SDK generation.

import AWSCore
import AWSAPIGateway

public class SVTLambdaGateClient: AWSAPIGatewayClient {

 static let AWSInfoClientKey = "SVTLambdaGateClient"

 private static let _serviceClients = AWSSynchronizedMutableDictionary()
 private static let _defaultClient:SVTLambdaGateClient = 
 var serviceConfiguration: AWSServiceConfiguration? = nil
 let serviceInfo = AWSInfo.default().defaultServiceInfo(AWSInfoClientKey)
 if let serviceInfo = serviceInfo 
 serviceConfiguration = AWSServiceConfiguration(region: serviceInfo.region, credentialsProvider: serviceInfo.cognitoCredentialsProvider)
 else if (AWSServiceManager.default().defaultServiceConfiguration != nil) 
 serviceConfiguration = AWSServiceManager.default().defaultServiceConfiguration
 else 
 serviceConfiguration = AWSServiceConfiguration(region: .Unknown, credentialsProvider: nil)
 

 return SVTLambdaGateClient(configuration: serviceConfiguration!)
 ()

 /**
 Returns the singleton service client. If the singleton object does not exist, the SDK instantiates the default service client with `defaultServiceConfiguration` from `AWSServiceManager.defaultServiceManager()`. The reference to this object is maintained by the SDK, and you do not need to retain it manually.
 @return The default service client.
 */ 

 public class func `default`() -> SVTLambdaGateClient
 return _defaultClient
 

 /**
 Creates a service client with the given service configuration and registers it for the key.
 @param configuration A service configuration object.
 @param key A string to identify the service client.
 */

 public class func registerClient(withConfiguration configuration: AWSServiceConfiguration, forKey key: String)
 _serviceClients.setObject(SVTLambdaGateClient(configuration: configuration), forKey: key as NSString);
 

 /**
 Retrieves the service client associated with the key. You need to call `registerClient(withConfiguration:configuration, forKey:)` before invoking this method or alternatively, set the configuration in your application's `info.plist` file. If `registerClientWithConfiguration(configuration, forKey:)` has not been called in advance or if a configuration is not present in the `info.plist` file of the app, this method returns `nil`.
 Then call the following to get the service client:

 let serviceClient = SVTLambdaGateClient.client(forKey: "USWest2SVTLambdaGateClient")

 @param key A string to identify the service client.
 @return An instance of the service client.
 */
 public class func client(forKey key: String) -> SVTLambdaGateClient 
 objc_sync_enter(self)
 if let client: SVTLambdaGateClient = _serviceClients.object(forKey: key) as? SVTLambdaGateClient 
 objc_sync_exit(self)
 return client
 

 let serviceInfo = AWSInfo.default().defaultServiceInfo(AWSInfoClientKey)
 if let serviceInfo = serviceInfo 
 let serviceConfiguration = AWSServiceConfiguration(region: serviceInfo.region, credentialsProvider: serviceInfo.cognitoCredentialsProvider)
 SVTLambdaGateClient.registerClient(withConfiguration: serviceConfiguration!, forKey: key)
 
 objc_sync_exit(self)
 return _serviceClients.object(forKey: key) as! SVTLambdaGateClient;
 

 /**
 Removes the service client associated with the key and release it.

 @param key A string to identify the service client.
 */
 public class func removeClient(forKey key: String) -> Void
 _serviceClients.remove(key)
 

 init(configuration: AWSServiceConfiguration) 
 super.init()

 self.configuration = configuration.copy() as! AWSServiceConfiguration
 var URLString: String = "https://<my-api-id>.execute-api.us-east-2.amazonaws.com/test"
 if URLString.hasSuffix("/") 
 URLString = URLString.substring(to: URLString.index(before: URLString.endIndex))
 
 self.configuration.endpoint = AWSEndpoint(region: configuration.regionType, service: .APIGateway, url: URL(string: URLString))
 let signer: AWSSignatureV4Signer = AWSSignatureV4Signer(credentialsProvider: configuration.credentialsProvider, endpoint: self.configuration.endpoint)
 if let endpoint = self.configuration.endpoint 
 self.configuration.baseURL = endpoint.url
 
 self.configuration.requestInterceptors = [AWSNetworkingRequestInterceptor(), signer]
 

 /*


 @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>
 


 /*


 @param body 

 return type: Empty
 */
 public func calcPost(body: SVTInput) -> AWSTask<Empty> 
 let headerParameters = [
 "Content-Type": "application/json",
 "Accept": "application/json",

 ]

 let queryParameters:[String:Any] = [:]

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

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


 /*


 @param operand2 
 @param _operator 
 @param operand1 

 return type: SVTResult
 */
 public func calcOperand1Operand2OperatorGet(operand2: String, _operator: String, operand1: String) -> AWSTask<SVTResult> 
 let headerParameters = [
 "Content-Type": "application/json",
 "Accept": "application/json",

 ]

 let queryParameters:[String:Any] = [:]

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

 return self.invokeHTTPRequest("GET", urlString: "/calc/operand1/operand2/operator", pathParameters: pathParameters, queryParameters: queryParameters, headerParameters: headerParameters, body: nil, responseClass: SVTResult.self) as! AWSTask<SVTResult>
 

Any help greatly appreciated!

The Amplify team (who maintain and develop the AWS iOS SDK) verified that the documentation is incorrect. It should reference default() and not defaultClient().