# Use iOS SDK generated by API Gateway for a REST API in Objective-C or Swift


In this tutorial, we will show how to use an iOS SDK generated by API Gateway for a REST API in an Objective-C or Swift app to call the underlying API. We will use the [SimpleCalc API](simple-calc-lambda-api.md) as an example to illustrate the following topics:
+ How to install the required AWS Mobile SDK components into your Xcode project
+ How to create the API client object before calling the API's methods
+ How to call the API methods through the corresponding SDK methods on the API client object
+ How to prepare a method input and parse its result using the corresponding model classes of the SDK

**Topics**
+ [

## Use generated iOS SDK (Objective-C) to call API
](#how-to-use-sdk-ios-objc)
+ [

## Use generated iOS SDK (Swift) to call API
](#how-to-generate-sdk-ios-swift)

## Use generated iOS SDK (Objective-C) to call API
Use generated iOS SDK (Objective-C) to call API

Before beginning the following procedure, you must complete the steps in [Generate SDKs for REST APIs in API Gateway](how-to-generate-sdk.md) for iOS in Objective-C and download the .zip file of the generated SDK.

### Install the AWS mobile SDK and an iOS SDK generated by API Gateway in an Objective-C project


The following procedure describes how to install the SDK.

**To install and use an iOS SDK generated by API Gateway in Objective-C**

1. Extract the contents of the API Gateway-generated .zip file you downloaded earlier. Using the [SimpleCalc API](simple-calc-lambda-api.md), you may want to rename the unzipped SDK folder to something like **sdk\$1objc\$1simple\$1calc**. In this SDK folder there is a `README.md` file and a `Podfile` file. The `README.md` file contains the instructions to install and use the SDK. This tutorial provides details about these instructions. The installation leverages [CocoaPods](https://cocoapods.org) to import required API Gateway libraries and other dependent AWS Mobile SDK components. You must update the `Podfile` to import the SDKs into your app's Xcode project. The unarchived SDK folder also contains a `generated-src` folder that contains the source code of the generated SDK of your API.

1. Launch Xcode and create a new iOS Objective-C project. Make a note of the project's target. You will need to set it in the `Podfile`.

      
![\[Find the target in Xcode.\]](http://docs.aws.amazon.com/apigateway/latest/developerguide/images/use-sdk-in-ios-objc-project-find-target.png)

1. To import the AWS Mobile SDK for iOS into the Xcode project by using CocoaPods, do the following:

   1. Install CocoaPods by running the following command in a terminal window:

      ```
      sudo gem install cocoapods
      pod setup
      ```

   1. Copy the `Podfile` file from the extracted SDK folder into the same directory containing your Xcode project file. Replace the following block:

      ```
      target '<YourXcodeTarget>' do
          pod 'AWSAPIGateway', '~> 2.4.7'
      end
      ```

      with your project's target name: 

      ```
      target 'app_objc_simple_calc' do
          pod 'AWSAPIGateway', '~> 2.4.7'
      end
      ```

      If your Xcode project already contains a file named `Podfile`, add the following line of code to it:

      ```
      pod 'AWSAPIGateway', '~> 2.4.7'
      ```

   1. Open a terminal window and run the following command:

      ```
      pod install
      ```

      This installs the API Gateway component and other dependent AWS Mobile SDK components.

   1. Close the Xcode project and then open the `.xcworkspace` file to relaunch Xcode.

   1. Add all of the `.h` and `.m` files from the extracted SDK's `generated-src` directory into your Xcode project.

         
![\[.h and .m files are in the generated-src\]](http://docs.aws.amazon.com/apigateway/latest/developerguide/images/use-sdk-in-ios-objc-project-add-sdk-src.png)

   To import the AWS Mobile SDK for iOS Objective-C into your project by explicitly downloading AWS Mobile SDK or using [Carthage](https://github.com/Carthage/Carthage#installing-carthage), follow the instructions in the *README.md* file. Be sure to use only one of these options to import the AWS Mobile SDK.

### Call API methods using the iOS SDK generated by API Gateway in an Objective-C project


When you generated the SDK with the prefix of `SIMPLE_CALC` for this [SimpleCalc API](simple-calc-lambda-api.md) with two models for input (`Input`) and output (`Result`) of the methods, in the SDK, the resulting API client class becomes `SIMPLE_CALCSimpleCalcClient` and the corresponding data classes are `SIMPLE_CALCInput` and `SIMPLE_CALCResult`, respectively. The API requests and responses are mapped to the SDK methods as follows:
+ The API request of

  ```
  GET /?a=...&b=...&op=...
  ```

  becomes the SDK method of

  ```
  (AWSTask *)rootGet:(NSString *)op a:(NSString *)a b:(NSString *)b
  ```

  The `AWSTask.result` property is of the `SIMPLE_CALCResult` type if the `Result` model was added to the method response. Otherwise, the property is of the `NSDictionary` type.
+ This API request of

  ```
  POST /
      
  {
     "a": "Number",
     "b": "Number",
     "op": "String"
  }
  ```

  becomes the SDK method of

  ```
  (AWSTask *)rootPost:(SIMPLE_CALCInput *)body
  ```
+ The API request of

  ```
  GET /{a}/{b}/{op}
  ```

  becomes the SDK method of

  ```
  (AWSTask *)aBOpGet:(NSString *)a b:(NSString *)b op:(NSString *)op
  ```

The following procedure describes how to call the API methods in Objective-C app source code; for example, as part of the `viewDidLoad` delegate in a `ViewController.m` file.

**To call the API through the iOS SDK generated by API Gateway**

1. Import the API client class header file to make the API client class callable in the app:

   ```
   #import "SIMPLE_CALCSimpleCalc.h"
   ```

   The `#import` statement also imports `SIMPLE_CALCInput.h` and `SIMPLE_CALCResult.h` for the two model classes.

1. Instantiate the API client class:

   ```
   SIMPLE_CALCSimpleCalcClient *apiInstance = [SIMPLE_CALCSimpleCalcClient defaultClient];
   ```

   To use Amazon Cognito with the API, set the `defaultServiceConfiguration` property on the default `AWSServiceManager` object, as shown in the following, before calling the `defaultClient` method to create the API client object (shown in the preceding example):

   ```
   AWSCognitoCredentialsProvider *creds = [[AWSCognitoCredentialsProvider alloc] initWithRegionType:AWSRegionUSEast1 identityPoolId:your_cognito_pool_id];
   AWSServiceConfiguration *configuration = [[AWSServiceConfiguration alloc] initWithRegion:AWSRegionUSEast1 credentialsProvider:creds];
   AWSServiceManager.defaultServiceManager.defaultServiceConfiguration = configuration;
   ```

1. Call the `GET /?a=1&b=2&op=+` method to perform `1+2`:

   ```
   [[apiInstance rootGet: @"+" a:@"1" b:@"2"] continueWithBlock:^id _Nullable(AWSTask * _Nonnull task) {
       _textField1.text = [self handleApiResponse:task];
       return nil;
   }];
   ```

   where the helper function `handleApiResponse:task` formats the result as a string to be displayed in a text field (`_textField1`).

   ```
   - (NSString *)handleApiResponse:(AWSTask *)task {
       if (task.error != nil) {
           return [NSString stringWithFormat: @"Error: %@", task.error.description];
       } else if (task.result != nil && [task.result isKindOfClass:[SIMPLE_CALCResult class]]) {
           return [NSString stringWithFormat:@"%@ %@ %@ = %@\n",task.result.input.a, task.result.input.op, task.result.input.b, task.result.output.c];
       }
       return nil;
   }
   ```

   The resulting display is `1 + 2 = 3`.

1. Call the `POST /` with a payload to perform `1-2`:

   ```
   SIMPLE_CALCInput *input = [[SIMPLE_CALCInput alloc] init];
       input.a = [NSNumber numberWithInt:1];
       input.b = [NSNumber numberWithInt:2];
       input.op = @"-";
       [[apiInstance rootPost:input] continueWithBlock:^id _Nullable(AWSTask * _Nonnull task) {
           _textField2.text = [self handleApiResponse:task];
           return nil;
       }];
   ```

   The resulting display is `1 - 2 = -1`.

1. Call the `GET /{a}/{b}/{op}` to perform `1/2`:

   ```
   [[apiInstance aBOpGet:@"1" b:@"2" op:@"div"] continueWithBlock:^id _Nullable(AWSTask * _Nonnull task) {
       _textField3.text = [self handleApiResponse:task];
       return nil;
   }];
   ```

   The resulting display is `1 div 2 = 0.5`. Here, `div` is used in place of `/` because the [simple Lambda function](simple-calc-nodejs-lambda-function.md) in the backend does not handle URL encoded path variables.

## Use generated iOS SDK (Swift) to call API
Use generated iOS SDK (Swift) to call API

Before beginning the following procedure, you must complete the steps in [Generate SDKs for REST APIs in API Gateway](how-to-generate-sdk.md) for iOS in Swift and download the .zip file of the generated SDK.

**Topics**
+ [

### Install AWS mobile SDK and API Gateway-generated SDK in a Swift project
](#use-sdk-ios-swift-install-sdk)
+ [

### Call API methods through the iOS SDK generated by API Gateway in a Swift project
](#use-sdk-ios-swift-call-api)

### Install AWS mobile SDK and API Gateway-generated SDK in a Swift project


The following procedure describes how to install the SDK.

**To install and use an iOS SDK generated by API Gateway in Swift**

1. Extract the contents of the API Gateway-generated .zip file you downloaded earlier. Using the [SimpleCalc API](simple-calc-lambda-api.md), you may want to rename the unzipped SDK folder to something like **sdk\$1swift\$1simple\$1calc**. In this SDK folder there is a `README.md` file and a `Podfile` file. The `README.md` file contains the instructions to install and use the SDK. This tutorial provides details about these instructions. The installation leverages [CocoaPods](https://cocoapods.org) to import required AWS Mobile SDK components. You must update the `Podfile` to import the SDKs into your Swift app's Xcode project. The unarchived SDK folder also contains a `generated-src` folder that contains the source code of the generated SDK of your API.

1. Launch Xcode and create a new iOS Swift project. Make a note of the project's target. You will need to set it in the `Podfile`.

      
![\[Find the target in Xcode.\]](http://docs.aws.amazon.com/apigateway/latest/developerguide/images/use-sdk-in-ios-swift-project-find-target.png)

1. To import the required AWS Mobile SDK components into the Xcode project by using CocoaPods, do the following:

   1. If it is not installed, install CocoaPods by running the following command in a terminal window:

      ```
      sudo gem install cocoapods
      pod setup
      ```

   1. Copy the `Podfile` file from the extracted SDK folder into the same directory containing your Xcode project file. Replace the following block:

      ```
      target '<YourXcodeTarget>' do
          pod 'AWSAPIGateway', '~> 2.4.7'
      end
      ```

      with your project's target name as shown: 

      ```
      target 'app_swift_simple_calc' do
          pod 'AWSAPIGateway', '~> 2.4.7'
      end
      ```

      If your Xcode project already contains a `Podfile` with the correct target, you can simply add the following line of code to the `do ... end` loop:

      ```
      pod 'AWSAPIGateway', '~> 2.4.7'
      ```

   1. Open a terminal window and run the following command in the app directory:

      ```
      pod install
      ```

      This installs the API Gateway component and any dependent AWS Mobile SDK components into the app's project.

   1. Close the Xcode project and then open the `*.xcworkspace` file to relaunch Xcode.

   1. Add all of the SDK's header files (`.h`) and Swift source code files (`.swift`) from the extracted `generated-src` directory to your Xcode project.

         
![\[.h and .swift files are in the generated-src\]](http://docs.aws.amazon.com/apigateway/latest/developerguide/images/use-sdk-in-ios-swift-project-add-sdk-src.png)

   1. To enable calling the Objective-C libraries of the AWS Mobile SDK from your Swift code project, set the `Bridging_Header.h` file path on the **Objective-C Bridging Header** property under the **Swift Compiler - General** setting of your Xcode project configuration: 

         
![\[Set the Bridging_Header.h file path under the Swift Compiler - General.\]](http://docs.aws.amazon.com/apigateway/latest/developerguide/images/use-sdk-in-ios-swift-project-set-bridging-header.png)
**Tip**  
You can type **bridging** in the search box of Xcode to locate the **Objective-C Bridging Header** property.

   1. Build the Xcode project to verify that it is properly configured before proceeding further. If your Xcode uses a more recent version of Swift than the one supported for the AWS Mobile SDK, you will get Swift compiler errors. In this case, set the **Use Legacy Swift Language Version** property to **Yes** under the **Swift Compiler - Version** setting:

         
![\[Set the Legacy Swift Language Version property to Yes.\]](http://docs.aws.amazon.com/apigateway/latest/developerguide/images/use-sdk-in-ios-swift-project-set-legacy-swift-version.png)

   To import the AWS Mobile SDK for iOS in Swift into your project by explicitly downloading the AWS Mobile SDK or using [Carthage](https://github.com/Carthage/Carthage#installing-carthage), follow the instructions in the `README.md` file that comes with the SDK package. Be sure to use only one of these options to import the AWS Mobile SDK.

### Call API methods through the iOS SDK generated by API Gateway in a Swift project


When you generated the SDK with the prefix of `SIMPLE_CALC` for this [SimpleCalc API](simple-calc-lambda-api.md) with two models to describe the input (`Input`) and output (`Result`) of the API's requests and responses, in the SDK, the resulting API client class becomes `SIMPLE_CALCSimpleCalcClient` and the corresponding data classes are `SIMPLE_CALCInput` and `SIMPLE_CALCResult`, respectively. The API requests and responses are mapped to the SDK methods as follows: 
+ The API request of

  ```
  GET /?a=...&b=...&op=...
  ```

  becomes the SDK method of

  ```
  public func rootGet(op: String?, a: String?, b: String?) -> AWSTask
  ```

  The `AWSTask.result` property is of the `SIMPLE_CALCResult` type if the `Result` model was added to the method response. Otherwise, it is of the `NSDictionary` type.
+ This API request of

  ```
  POST /
      
  {
     "a": "Number",
     "b": "Number",
     "op": "String"
  }
  ```

  becomes the SDK method of

  ```
  public func rootPost(body: SIMPLE_CALCInput) -> AWSTask
  ```
+ The API request of

  ```
  GET /{a}/{b}/{op}
  ```

  becomes the SDK method of

  ```
  public func aBOpGet(a: String, b: String, op: String) -> AWSTask
  ```

The following procedure describes how to call the API methods in Swift app source code; for example, as part of the `viewDidLoad()` delegate in a `ViewController.m` file.

**To call the API through the iOS SDK generated by API Gateway**

1. Instantiate the API client class:

   ```
   let client = SIMPLE_CALCSimpleCalcClient.default()
   ```

   To use Amazon Cognito with the API, set a default AWS service configuration (shown following) before getting the `default` method (shown previously):

   ```
   let credentialsProvider = AWSCognitoCredentialsProvider(regionType: AWSRegionType.USEast1, identityPoolId: "my_pool_id")        
   let configuration = AWSServiceConfiguration(region: AWSRegionType.USEast1, credentialsProvider: credentialsProvider)        
   AWSServiceManager.defaultServiceManager().defaultServiceConfiguration = configuration
   ```

1. Call the `GET /?a=1&b=2&op=+` method to perform `1+2`:

   ```
   client.rootGet("+", a: "1", b:"2").continueWithBlock {(task: AWSTask) -> AnyObject? in
       self.showResult(task)
       return nil
   }
   ```

   where the helper function `self.showResult(task)` prints the result or error to the console; for example: 

   ```
   func showResult(task: AWSTask) {
       if let error = task.error {
           print("Error: \(error)")
       } else if let result = task.result {
           if result is SIMPLE_CALCResult {
               let res = result as! SIMPLE_CALCResult
               print(String(format:"%@ %@ %@ = %@", res.input!.a!, res.input!.op!, res.input!.b!, res.output!.c!))
           } else if result is NSDictionary {
               let res = result as! NSDictionary
               print("NSDictionary: \(res)")
           }
       }
   }
   ```

   In a production app, you can display the result or error in a text field. The resulting display is `1 + 2 = 3`.

1. Call the `POST /` with a payload to perform `1-2`:

   ```
   let body = SIMPLE_CALCInput()
   body.a=1
   body.b=2
   body.op="-"
   client.rootPost(body).continueWithBlock {(task: AWSTask) -> AnyObject? in
       self.showResult(task)
       return nil
   }
   ```

   The resultant display is `1 - 2 = -1`.

1. Call the `GET /{a}/{b}/{op}` to perform `1/2`:

   ```
   client.aBOpGet("1", b:"2", op:"div").continueWithBlock {(task: AWSTask) -> AnyObject? in
       self.showResult(task)
       return nil
   }
   ```

   The resulting display is `1 div 2 = 0.5`. Here, `div` is used in place of `/` because the [simple Lambda function](simple-calc-nodejs-lambda-function.md) in the backend does not handle URL encoded path variables.