Fetch data

GET requests

To make a GET request, first create a RESTRequest object and then use the Amplify.API.get api to issue the request:

func getTodo() {
    let request = RESTRequest(path: "/todo")
    Amplify.API.get(request: request) { result in
        switch result {
        case .success(let data):
            let str = String(decoding: data, as: UTF8.self)
            print("Success \(str)")
        case .failure(let apiError):
            print("Failed", apiError)
        }
    }
}

func getTodo() -> AnyCancellable {
    let request = RESTRequest(path: "/todo")
    let sink = Amplify.API.get(request: request)
        .resultPublisher
        .sink {
            if case let .failure(apiError) = $0 {
                print("Failed", apiError)
            }
        }
        receiveValue: { data in
            let str = String(decoding: data, as: UTF8.self)
            print("Success \(str)")
        }
    return sink
}

Handling non-2xx HTTP responses

When your service returns a non-2xx HTTP status code in the response, the API call will result in a failure that you can handle in your app. The response body can be accessed from the body: Data? property. For example, when the APIError is an .httpStatusError(StatusCode, HTTPURLResponse), then access the response body by type casting the response to an AWSHTTPURLResponse and retrieve the body field.

if case let .httpStatusError(statusCode, response) = error,
    let awsResponse = response as? AWSHTTPURLResponse,
    let responseBody = awsResponse.body
{
    print("Response contains a \(responseBody.count) byte long response body")
}

Accessing query parameters & body in Lambda proxy function

To learn more about Lambda Proxy Integration, please visit Amazon API Gateway Developer Guide.

If you are using a REST API which is generated with Amplify CLI, your backend is created with Lambda Proxy Integration, and you can access your query parameters & body within your Lambda function via the event object:

exports.handler = function(event, context, callback) {
    console.log(event.queryStringParameters);
    console.log('body: ', event.body);
}

Alternatively, you can update your backend file which is located at amplify/backend/function/[your-lambda-function]/app.js with the middleware:

const awsServerlessExpressMiddleware = require('aws-serverless-express/middleware');
app.use(awsServerlessExpressMiddleware.eventContext());

Accessing query parameters with Serverless Express

In your request handler use req.apiGateway.event or req.query:

app.get('/todo', function(req, res) {
  const query = req.query;
  // or
  // const query = req.apiGateway.event.queryStringParameters
  res.json({
    event: req.apiGateway.event, // to view all event data
    query: query
  });
});

Then you can use query parameters in your path as follows:

func getTodo() {
    let queryParameters = ["q":"test"]
    let request = RESTRequest(path: "/todo", queryParameters: queryParameters)
    Amplify.API.get(request: request) { result in
        switch result {
        case .success(let data):
            let str = String(decoding: data, as: UTF8.self)
            print("Success \(str)")
        case .failure(let apiError):
            print("Failed", apiError)
        }
    }
}

func getTodo() -> AnyCancellable {
    let queryParameters = ["q":"test"]
    let request = RESTRequest(path: "/todo", queryParameters: queryParameters)
    let sink = Amplify.API.get(request: request)
        .resultPublisher
        .sink {
            if case let .failure(apiError) = $0 {
                print("Failed", apiError)
            }
        }
        receiveValue: { data in
            let str = String(decoding: data, as: UTF8.self)
            print("Success \(str)")
        }
    return sink
}