How to upload files to S3 from iOS app written in Objective C using AWS Cognito identity pool

Background

This post assumes you have setup Cognito identity pool as explained in the previous post -

• How to setup Cognito Identity Pool for unauthenticated or authenticated access to AWS resources like S3

If not, then please refer the previous post and set that up. Before starting with using this you should have -

1. Identity pool ID
2. AWS region where pool and S3 bucket reside
3. S3 bucket name

We will use above in configuration and implementation that follows.

How to upload files to S3 from iOS app written in Objective C using AWS Cognito identity pool

• First, go to your pod file and update following dependencies -

# Uncomment the next line to define a global platform for your project
# platform :ios, '9.0'


target 'TestApp' do
  # Uncomment the next line if you're using Swift or would like to use dynamic frameworks
  # use_frameworks!
  # Pods for TestApp


pod 'AWSMobileClient', '~> 2.6.18'  # For AWSMobileClient
pod 'AWSS3', '~> 2.6.18'            # For file transfers
pod 'AWSCognito', '~> 2.6.18'       # For data sync

end

• Next run "Run pod install --repo-update" from the command line
• Once you have the dependencies installed we can now write Objective C code to upload a file to S3.

//
//  FileUploader.m
//  TestApp
//
//  Created by Aniket on 22/05/18.
//


#import <Foundation/Foundation.h>


#import "FileUploader.h"
#import <AWSS3/AWSS3.h>
#import <AWSCore/AWSCore.h>




@implementation FileUploader


static AWSS3TransferManager *transferManager;


+ (void) initialize {
    
    if (self == [FileUploader class]) {
        AWSCognitoCredentialsProvider *credentialsProvider = [[AWSCognitoCredentialsProvider alloc] initWithRegionType:AWSRegionUSEast1 identityPoolId:@"us-east-1:f847843f-0162-43c2-b73f-efdc7c69cce2"];
        AWSServiceConfiguration *configuration = [[AWSServiceConfiguration alloc] initWithRegion:AWSRegionUSEast1 credentialsProvider:credentialsProvider];
        [AWSS3TransferManager registerS3TransferManagerWithConfiguration:[[AWSServiceConfiguration alloc] initWithRegion:AWSRegionUSEast1 credentialsProvider:credentialsProvider] forKey:s3TransferManagerKey];


        AWSServiceManager.defaultServiceManager.defaultServiceConfiguration = configuration;
                                        
        transferManager = [AWSS3TransferManager S3TransferManagerForKey:s3TransferManagerKey];
    }
    
}


+ (void)uploadFile
{
    
    
    NSURL *uploadingFileURL = [NSURL fileURLWithPath: @"PATH_TO_FILE";
    AWSS3TransferManagerUploadRequest *uploadRequest = [AWSS3TransferManagerUploadRequest new];
    
    
    uploadRequest.bucket = s3Bucket;
    int timestamp = [[NSDate date] timeIntervalSince1970];
    uploadRequest.key = [NSString stringWithFormat:@"%@-%d%@",@"testfile",timestamp,@".txt"];
    uploadRequest.body = uploadingFileURL;
    
    [[transferManager upload:uploadRequest] continueWithExecutor:[AWSExecutor mainThreadExecutor]
                                                       withBlock:^id(AWSTask *task) {
                                                           if (task.error) {
                                                               if ([task.error.domain isEqualToString:AWSS3TransferManagerErrorDomain]) {
                                                                   switch (task.error.code) {
                                                                       case AWSS3TransferManagerErrorCancelled:
                                                                       case AWSS3TransferManagerErrorPaused:
                                                                           break;
                                                                           
                                                                       default:
                                                                           NSLog(@"Error uploading file to S3: %@", task.error);
                                                                           break;
                                                                   }
                                                               } else {
                                                                   // Unknown error.
                                                                   NSLog(@"Error uploading file to S3: %@", task.error);
                                                               }
                                                           }
                                                           
                                                           if (task.result) {
                                                               AWSS3TransferManagerUploadOutput *uploadOutput = task.result;
                                                               // The file uploaded successfully.
                                                               NSLog(@"uploading file to S3 was successful: %@", uploadOutput);
                                                           }
                                                           return nil;
                                                       }];
    
}
@end

In above code replace the identity pool id and region as per your configuration settings. This is Objective C code, if you want to see Swift or Android - Java please refer https://docs.aws.amazon.com/aws-mobile/latest/developerguide/how-to-integrate-an-existing-bucket.html

Related Links

• How to setup Cognito Identity Pool for unauthenticated or authenticated access to AWS resources like S3(OSFG)
• https://docs.aws.amazon.com/aws-mobile/latest/developerguide/how-to-integrate-an-existing-bucket.html