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Use an iOS SDK generated by API Gateway in an Objective-C App

Before beginning the following procedure, you must complete the steps in Generate SDKs for an API Using the API Gateway Console 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, you may want to rename the unzipped SDK folder to something like sdk_objc_simple_calc. 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 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.

  2. 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.

  3. 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:

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      sudo gem install cocoapods pod setup
    2. Copy the Podfile file from the extracted SDK folder into the same directory containing your Xcode project file. Replace the following block:

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

      with your project's target name:

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      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:

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      pod 'AWSAPIGateway', '~> 2.4.7'
    3. Open a terminal window and run the following command:

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      pod install

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

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

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

    To import the AWS Mobile SDK for iOS Objective-C into your project by explicitly downloading AWS Mobile SDK or using 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 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

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

    becomes the SDK method of

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    (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

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

    becomes the SDK method of

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

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

    becomes the SDK method of

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    (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:

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    #import "SIMPLE_CALCSimpleCalc.h"

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

  2. Instantiate the API client class:

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    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):

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    AWSCognitoCredentialsProvider *creds = [[AWSCognitoCredentialsProvider alloc] initWithRegionType:AWSRegionUSEast1 identityPoolId:your_cognito_pool_id]; AWSServiceConfiguration *configuration = [[AWSServiceConfiguration alloc] initWithRegion:AWSRegionUSEast1 credentialsProvider:creds]; AWSServiceManager.defaultServiceManager.defaultServiceConfiguration = configuration;
  3. Call the GET /?a=1&b=2&op=+ method to perform 1+2:

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    [[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).

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    - (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.

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

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    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.

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

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    [[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 in the back end does not handle URL encoded path variables.