How to call an AWS webservice (API Gateway) on iOS using SOTO?

Question

In my iOS project, I need to implement the AWS SDK, as I successfully did in the Android version of that project, if possible using Swift Package Manager and not Cocoapods.

Since it doesn't seem to be available yet for SPM, I tried Soto, that allows me to implement the AWS SDK using SPM.

Here is what I did in my Android project, that I want to replicate on iOS:

• I created an AWSInterface interface, where all my api endpoints are:

@Service(endpoint = "https://abcde12345.execute-api.eu-central-1.amazonaws.com/dev")
interface AWSInterface
{
    @Operation(path = "/api-demo", method = "POST")
    fun apiDemo(
        @Parameter(name = "Content-Type", location = "header") contentType: String,
        body: ApiDemoModel): RetourStatutWS
}

• and here is the ApiDemoModel, very simple:

class ApiDemoModel(val code: String)

• I created an AWSInterfaceHolder class, so I'll be able to call apis:

class AWSInterfaceHolder {

    var awsInterface: AWSInterface = ApiClientFactory()
        .credentialsProvider(AWSMobileClient.getInstance())
        .clientConfiguration(ClientConfiguration().withConnectionTimeout(30000))
        .build(AWSInterface::class.java)
}

• I initialized AWSMobileClient, and call my api:

AWSMobileClient.getInstance().initialize(
    applicationContext,
    object : Callback<UserStateDetails> {

        override fun onResult(result: UserStateDetails?) {
            
            // AWSMobileClient is successfully initialized, I can call my api:
            val awsInterfaceHolder = AWSInterfaceHolder()
             awsInterfaceHolder.awsInterface.apiDemo(
                 "application/json",
                 ApiDemoModel("123456"))
        }

        override fun onError(e: Exception?) {
            e.printStackTrace()
        }
}

How can I do the same for my iOS Swift project, if possible using Soto, since the default AWS SDK is not available for SPM yet?

Thanks.

Answer 1

Soto doesn't have any code generation for APIGateway but if you are looking to sign requests for an APIGateway REST interface you could do the following. The code uses the swift-server AsyncHTTPClient but it should be easy enough to translate the results of the signHeaders to a URLRequest for use with a URLSession.

import SotoSignerV4

func apiGatewayExecute(
    url: URL, 
    method: HTTPMethod, 
    headers: HTTPHeaders, 
    body: ByteBuffer? = nil
) -> EventLoopFuture<HTTPClient.Response> {
    let credentials: Credential = StaticCredential(
        accessKeyId: "_MYACCESSKEY_", 
        secretAccessKey: "_MYSECRETACCESSKEY_"
    )
    let signer = AWSSigner(credentials: credentials, name: "execute-api", region: "us-east-1")
    // clean up URL
    let processedURL = signer.processURL(url: url)!
    let signedHeaders = signer.signHeaders(
        url: processedURL,
        method: method,
        headers: headers,
        body: body.map { .byteBuffer($0) }
    )
    let request = try! HTTPClient.Request(
        url: processedURL,
        method: method,
        headers: signedHeaders,
        body: body.map { .byteBuffer($0) }
    )
    return httpClient.execute(request: request, logger: logger)
}