Spotify Login Helper

JBSpotifyLoginViewController.h

//
//  JBSpotifyLoginViewController.h
//  JukeBox
//
//  Created by Andrei on 9/2/13.
//  Copyright (c) 2013 andreipatru. All rights reserved.
//

#import "SPLoginViewController.h"

@interface JBSpotifyLoginViewController : UIViewController <SPLoginViewControllerDelegate, SPSessionDelegate> {
}

@property (nonatomic, strong) SPLoginViewController *viewControllerSPLogin;
@property (nonatomic, strong) void (^successBlock)(SPSession *);
@property (nonatomic, strong) void (^failureBlock)(SPSession *, NSError *);
@property (nonatomic, strong) UIViewController *viewControllerCallingParent;

+ (BOOL)isLoggedIn;

- (id)init;
- (void)performLoginProcessFromViewController:(UIViewController *)modalParent
                             withSuccessBlock:(void (^)(SPSession *session))theSuccessBlock
                              andFailureBlock:(void (^)(SPSession *session, NSError *error))theFailBlock;

@end

JBSpotifyLoginViewController.m

//
//  JBSpotifyLoginViewController.m
//  JukeBox
//
//  Created by Andrei on 9/2/13.
//  Copyright (c) 2013 andreipatru. All rights reserved.
//

#import <Parse/Parse.h>

#import "JBSpotifyLoginViewController.h"

@interface JBSpotifyLoginViewController ()

@end

@implementation JBSpotifyLoginViewController

- (id)init {
    self = [super init];
    
    if (self) {
        self.viewControllerSPLogin = [SPLoginViewController loginControllerForSession:[SPSession sharedSession]];
        
        if ([self respondsToSelector:@selector(edgesForExtendedLayout)]) {
            self.viewControllerSPLogin.edgesForExtendedLayout = UIRectEdgeNone;
        }
        
        self.viewControllerSPLogin.loginDelegate = self;
        self.viewControllerSPLogin.dismissesAfterLogin = YES;
        [[SPSession sharedSession] setDelegate:self];
    }
    
    return self;
}

+ (BOOL)isLoggedIn {
    return ([SPSession sharedSession].connectionState == SP_CONNECTION_STATE_LOGGED_IN);
}

- (void)performLoginProcessFromViewController:(UIViewController *)modalParent
                             withSuccessBlock:(void (^)(SPSession *session))theSuccessBlock
                              andFailureBlock:(void (^)(SPSession *session, NSError *error))theFailBlock;
{
    self.viewControllerCallingParent = modalParent;
    self.successBlock = theSuccessBlock;
    self.failureBlock = theFailBlock;
    
    if ([JBSpotifyLoginViewController isLoggedIn]) {
        // a user is already logged in
        self.successBlock([SPSession sharedSession]);
    } else {
        // not logged in
        [modalParent presentViewController:self.viewControllerSPLogin
                                  animated:YES
                                completion:nil];
    }
}

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view.
    
    if ([self respondsToSelector:@selector(edgesForExtendedLayout)]) {
        self.edgesForExtendedLayout = UIRectEdgeNone;
    }
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - SPLoginViewControllerDelegate

/** Called when the login/signup process has completed.
 
 @param controller The SPLoginViewController instance that generated the message.
 @param didLogin `YES` if the user successfully logged in, otherwise `NO`..
 */
-(void)loginViewController:(SPLoginViewController *)controller didCompleteSuccessfully:(BOOL)didLogin {
    if (controller == self.viewControllerSPLogin) {
    }
}

#pragma mark - SPSessionDelegate

/** Called when a set of login credentials has been generated for the user, typically just after login.
 
 If you wish to store login credentials for multiple users, store the credentials given by this
 delegate method rather than their passwords (it's against the libSpotify Terms and Conditions to store
 Spotify passwords yourself). These credentials are safe to store without encryption, such as in `NSUserDefaults`.
 
 To use these credentials to log in, use `-attemptLoginWithUserName:existingCredential:rememberCredentials:`.
 
 @param aSession The session that logged in.
 @param credential The login credential.
 @param userName The username for the given credential.
 */
-(void)session:(SPSession *)aSession didGenerateLoginCredentials:(NSString *)credential forUserName:(NSString *)userName {
	// TODO: could be a good idea to save userName and credential in NSUserDefaults here
}

/** Called when the given session has logged in successfully.
 
 @param aSession The session that logged in.
 */
-(void)sessionDidLoginSuccessfully:(SPSession *)aSession {
    self.successBlock(aSession);

    if (self.viewControllerSPLogin.dismissesAfterLogin) {
        [self.viewControllerCallingParent dismissViewControllerAnimated:YES
                                                             completion:^{
                                                             }];
    }
}

/** Called when the given session could not log in successfully.
 
 @param aSession The session that failed to log in.
 @param error An NSError object describing the failure.
 */
-(void)session:(SPSession *)aSession didFailToLoginWithError:(NSError *)error {
    self.failureBlock(aSession, error);
}

@end

usage

    // ...
    
    JBSpotifyLoginViewController *loginController = [[JBSpotifyLoginViewController alloc] init];
    [loginController
     performLoginProcessFromViewController:self
     withSuccessBlock:^(SPSession *session) {
         // do stuff
     } andFailureBlock:^(SPSession *session, NSError *error) {
         NSLog(@"failed to log in");
     }];
     
     // ...