Using Twitter reverse_auth and Parse

example_using_twitter_reverse_auth_and_parse.m

- (void)signInWithTwitterAccount:(ACAccount *)account completion:(void (^)(Person *person, BOOL justSignedUp, NSError *error))completion {
        
    // Use Twitter's reverse auth to get the user credentials
    [TwitterHelper getCredentialsForAccount:account completion:^(NSDictionary *credentials, NSError *error) {

        // Now sign in using Parse
        [PFTwitterUtils logInWithTwitterId:(credentials)[TwitterCredentials.userId] screenName:(credentials)[TwitterCredentials.screenName] authToken:(credentials)[TwitterCredentials.oauthToken] authTokenSecret:(credentials)[TwitterCredentials.oauthTokenSecret] block:^(PFUser *user, NSError *error) {

            // Check if we've got a user
            if (user && !error) {
 
                // Do something interesting with a newly signed in user.
                Person *person = [Person personWithUser:user];

                completion(person, user.isNew, nil);

            } else {
                // Perform error handling
                completion(nil, NO, error);
            }
        }];
    }];

}

parse_geospatial_example_snippet.m

// Create a query
self.query = [PFQuery queryWithClassName:NSStringFromClass([GeoThings class])];

// Add the geo constraint
[self.query whereKey:@"location" withinGeoBoxFromSouthwest:southwest toNortheast:northeast];

// Order by timestamp
[self.query orderByDescending:@"timestamp"];

// Perform the query
[self.query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    
    // Do something cool with the objects

}];

parse_twitter_utils_header_snippet.m

+ (void)logInWithTwitterId:(NSString *)twitterId 
                screenName:(NSString *)screenName 
                 authToken:(NSString *)authToken 
           authTokenSecret:(NSString *)authTokenSecret 
                     block:(PFUserResultBlock)block;

TwitterHelper.h

//
//  TwitterHelper.h
//
//  Created by Daniel Thorpe on 23/05/2012.
//  Copyright (c) 2012 Blinding Skies Limited. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <ACAccounts/ACAccounts.h>

extern const struct TwitterCredentials {
    __unsafe_unretained NSString *oauthToken;
    __unsafe_unretained NSString *oauthTokenSecret;
    __unsafe_unretained NSString *userId;
    __unsafe_unretained NSString *screenName;
} TwitterCredentials;

@interface TwitterHelper : NSObject

+ (void)getCredentialsForAccount:(ACAccount *)account
                      completion:(void(^)(NSDictionary *credentials, NSError *error))completion;


@end

TwitterHelper.m

//
//  TwitterHelper.m
//
//  Created by Daniel Thorpe on 23/05/2012.
//  Copyright (c) 2012 Blinding Skies Limited. All rights reserved.
//

#import "STLOAuthClient.h"
#import "SecretKeys.h"
#import <Social/Social.h>

#import "DeviceHelper.h"
#import "TwitterHelper.h"

#define kTwitterApiRootURL [NSURL URLWithString:@"https://api.twitter.com/1/"]

const struct TwitterCredentials TwitterCredentials = {
    .oauthToken = @"oauth_token",
    .oauthTokenSecret = @"oauth_token_secret",
    .userId = @"user_id",
    .screenName = @"screen_name"
};

@implementation TwitterHelper

+ (void)getCredentialsForAccount:(ACAccount *)account completion:(void(^)(NSDictionary *credentials, NSError *error))completion {
    NSParameterAssert(completion);
    // Configure the URL
    NSURL *url = [NSURL URLWithString:@"https://api.twitter.com/"];
    
    // Create a client
    STLOAuthClient *client = [[STLOAuthClient alloc] initWithBaseURL:url consumerKey:kTwitterConsumerKey secret:kTwitterConsumerSecret];
    
    // Create other parameters
    NSDictionary *params = @{ @"x_auth_mode" : @"reverse_auth" };
    
    [client getPath:@"oauth/request_token" parameters:params success:^(AFHTTPRequestOperation *operation, id responseObject) {
        
        // Get the oauth response
        NSString *oauth = operation.responseString;
        
        // Configure the parameters
        NSDictionary *params = @{ @"x_reverse_auth_target" : kTwitterConsumerKey, @"x_reverse_auth_parameters" : oauth };
        
        // Get the URL
        NSURL *accessURL = [NSURL URLWithString:@"oauth/access_token" relativeToURL:url];

        // Create a request
        TWRequest *request = [[TWRequest alloc] initWithURL:accessURL parameters:params requestMethod:TWRequestMethodPOST];
            
        // Set the account
        request.account = account;            

        // Perform the request
        [request performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) {
            
            // Check for errors
            if (responseData && !error) {
                
                // Decode the response data into a string
                NSString *response = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];

                completion([TwitterHelper credentialsFromTwitterOAuthResponse:response], nil);
                
            } else {
                completion(nil, error);
            }
        }];
        
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        completion(nil, error);
    }];
}

+ (NSDictionary *)credentialsFromTwitterOAuthResponse:(NSString *)response {
    
    // Divide the string by ampersands
    NSArray *components = [response componentsSeparatedByString:@"&"];
    
    NSMutableDictionary *credentials = [NSMutableDictionary dictionaryWithCapacity:4];
    
    // Iterate through the components
    for (NSString *component in components) {
        
        // Split by = sign
        NSRange divider = [component rangeOfString:@"="];
        NSString *key = [component substringToIndex:divider.location];
        NSString *val = [component substringFromIndex:divider.location+1];
        [credentials setObject:val forKey:key];
    }
    
    return credentials;
}

@end