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 robb [email protected] ceterum_censeo

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Let's talk about ReactiveCocoa

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Let's talk about ReactiveCocoa state

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evil √

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Have you tried turning it off and on again?

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Have you tried turning it off and on again? Have you tried turning it off and on again?

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Start Okay Fail

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Start Okay Fail power-cycle power-cycle

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state

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state

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duh! " " you say

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e.g.

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@property (readwrite) BOOL walks;
 @property (readwrite) BOOL quaks; ! @property (readonly) BOOL duck;

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duck = walks ∧ quaks

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 ! ! - (void)setQuacks:(BOOL)quacks { _quacks = quacks; 
 self.duck = quacks && self.walks;
 } - ( _walks = walks; 
 self.duck = walks }

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- (BOOL)duck { return self.walks && self.quacks;
 } // duck = walks ∧ quaks

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ReactiveCocoa

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Functional Reactive
 Programming

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Signals instead of variables

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Pipes, not boxes

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wtf? " " you may be thinking

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e.g.

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RAC(self, duck) = [RACSignal
 combineLatest:@[
 RACObserve(self, walks),
 RACObserve(self, quacks)
 ]]
 reduce:^(NSNumber *walks, NSNumber *quacks) {
 return @(walks.boolValue &&
 quacks.boolValue);
 }];

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RAC(self, duck) = [RACSignal
 combineLatest:@[
 RACObserve(self, walks),
 RACObserve(self, quacks)
 ]]
 reduce:^(NSNumber *walks, NSNumber *quacks) {
 return @(walks.boolValue &&
 quacks.boolValue);
 }];

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RAC(self, duck) = [RACSignal
 combineLatest:@[
 RACObserve(self, walks),
 RACObserve(self, quacks)
 ]]
 reduce:^(NSNumber *walks, NSNumber *quacks) {
 return @(walks.boolValue &&
 quacks.boolValue);
 }];

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RAC(self, duck) = [RACSignal
 combineLatest:@[
 RACObserve(self, walks),
 RACObserve(self, quacks)
 ]]
 reduce:^(NSNumber *walks, NSNumber *quacks) {
 return @(walks.boolValue &&
 quacks.boolValue);
 }];

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& walks talks duck

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& walks talks duck

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& walks talks duck

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& walks talks duck

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& walks talks duck

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RACSignal

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-(RACDisposable *)subscribe:(id)obj; RACSignal

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- (void)sendNext:(id)value;

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- (void)sendNext:(id)value; - (void)sendCompleted;

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- (void)sendNext:(id)value; - (void)sendCompleted; - (void)sendError:(NSError *)error;

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so what?

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Powerful toolset

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map

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filter

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fold

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write declarative code

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e.g.

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Newsletter Your name Your email address Sign Up Brooklyn 4:00 PM 100%

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Newsletter Your email address Sign Up robb Brooklyn 4:00 PM 100%

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Newsletter Sign Up robb robb Brooklyn 4:00 PM 100%

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Newsletter Sign Up robb @robb.is Sign Up robb Brooklyn 4:00 PM 100%

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Your name Your email address Sign Up validate Newsletter

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Your name Your email address Sign Up validate that looks familiar! Newsletter

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- (void)viewDidLoad {
 [super viewDidLoad];
 [self.username
 addTarget:self
 action:@selector(textFieldTextDidChange:)
 forControlEvents:UIControlEventAllEditingEvents];
 [self.email
 addTarget:self
 action:@selector(textFieldTextDidChange:)
 forControlEvents:UIControlEventAllEditingEvents];
 } help!

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- (void)textFieldTextDidChange:(UITextField *)field {
 BOOL validUsername = self.username.text.length > 0;
 
 NSRange at = [self.email.text rangeOfString:@"@"];
 
 BOOL validEmail = at.location != NSNotFound;
 self.signupButton.enabled = validUsername &&
 validEmail;
 }

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- (void)textFieldTextDidChange:(UITextField *)field {
 BOOL validUsername = self.username.text.length > 0;
 
 NSRange at = [self.email.text rangeOfString:@"@"];
 
 BOOL validEmail = at.location != NSNotFound;
 self.signupButton.enabled = validUsername &&
 validEmail;
 }

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ReactiveCocoa

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 self.name.rac_textSignal
 self.email.rac_textSignal
 ]]
 reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"]; ! return @(at.location != NSNotFound && name.length > 0);
 }]:

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 self.name.rac_textSignal
 self.email.rac_textSignal
 ]]
 reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"]; ! return @(at.location != NSNotFound && name.length > 0);
 }]:

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 self.name.rac_textSignal
 self.email.rac_textSignal
 ]]
 reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"]; ! return @(at.location != NSNotFound && name.length > 0);
 }]:

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 self.name.rac_textSignal
 self.email.rac_textSignal
 ]]
 reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"]; ! return @(at.location != NSNotFound && name.length > 0);
 }]:

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Your name Your email address Sign Up validate Newsletter

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Newsletter Your name Your email address Sign Up Brooklyn 4:00 PM 100%

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Newsletter Your email address Sign Up robb Brooklyn 4:00 PM 100%

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Newsletter Sign Up robb Sign Up [email protected] Brooklyn 4:00 PM 100%

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Let's talk about Asynchrony

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[client logInWithSuccess:^{ [client loadMeUserWithSuccess:^(SPUser *me) { [client loadNewslettersForUser:me withSuccess:^(NSArray *newsletters) { NSLog(@"Help me, " "I'm trapped in callback hell!"); } error:^(NSError *error) { // Handle failure } } error:^(NSError *error) { // Handle failure }];
 } error:^(NSError *error) { // Handle failure }];

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[client logInWithSuccess:^{ [client loadMeUserWithSuccess:^(SPUser *me) { [client loadNewslettersForUser:me withSuccess:^(NSArray *newsletters) { NSLog(@"Help me, " "I'm trapped in callback hell!"); } error:^(NSError *error) { // Handle failure } } error:^(NSError *error) { // Handle failure }];
 } error:^(NSError *error) { // Handle failure }]; omg, why?!

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Let's fix this

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1. HTTP Client

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@interface SPHTTPClient : AFHTTPClient
 
 - (RACSignal *)enqueueRequest:(NSURLRequest *)req;
 
 @end

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[self enqueueHTTPRequestOperation:operation]; ! - (RACSignal *)enqueueRequest:(NSURLRequest *)req {
 return [RACSignal createSignal:^(id subscriber) { AFHTTPRequestOperation *operation; operation = [self HTTPRequestOperationWithRequest:req success:^(id operation, id response) { [subscriber sendNext:response]; [subscriber sendCompleted]; }} failure:^(id operation, NSError *error) { [subscriber sendError:error]; }];

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- (RACSignal *)enqueueRequest:(NSURLRequest *)req {
 return [RACSignal createSignal:^(id subscriber) { AFHTTPRequestOperation *operation; operation = [self HTTPRequestOperationWithRequest:req success:^(id operation, id response) { [subscriber sendNext:response]; [subscriber sendCompleted]; }} failure:^(id operation, NSError *error) { [subscriber sendError:error]; }]; [self enqueueHTTPRequestOperation:operation]; !

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[self enqueueHTTPRequestOperation:operation]; ! - (RACSignal *)enqueueRequest:(NSURLRequest *)req {
 return [RACSignal createSignal:^(id subscriber) { AFHTTPRequestOperation *operation; operation = [self HTTPRequestOperationWithRequest:req success:^(id operation, id response) { [subscriber sendNext:response]; [subscriber sendCompleted]; }} failure:^(id operation, NSError *error) { [subscriber sendError:error]; }];

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- (RACSignal *)enqueueRequest:(NSURLRequest *)req {
 return [RACSignal createSignal:^(id subscriber) { AFHTTPRequestOperation *operation; operation = [self HTTPRequestOperationWithRequest:req success:^(id operation, id response) { [subscriber sendNext:response]; [subscriber sendCompleted]; }} failure:^(id operation, NSError *error) { [subscriber sendError:error]; }]; [self enqueueHTTPRequestOperation:operation]; !

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- (RACSignal *)enqueueRequest:(NSURLRequest *)req {
 return [RACSignal createSignal:^(id subscriber) { AFHTTPRequestOperation *operation; operation = [self HTTPRequestOperationWithRequest:req success:^(id operation, id response) { [subscriber sendNext:response]; [subscriber sendCompleted]; }} failure:^(id operation, NSError *error) { [subscriber sendError:error]; }]; [self enqueueHTTPRequestOperation:operation]; !

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[self enqueueHTTPRequestOperation:operation]; ! return [RACDisposable disposableWithBlock:^{ [operation cancel]; }]; }]; success:^( [subscriber sendNext:response]; [subscriber sendCompleted]; } failure:^( [subscriber sendError:error]; }];

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[self enqueueHTTPRequestOperation:operation]; ! return [RACDisposable disposableWithBlock:^{ [operation cancel]; }]; }]; success:^( [subscriber sendNext:response]; [subscriber sendCompleted]; } failure:^( [subscriber sendError:error]; }];

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2. API interaction

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- (RACSignal *)fetchMeUser
 return [[self.client getPath:@"/me"] flattenMap:^(id JSON) { NSError *error; SPUser *user = [SPUser userWithJSON:JSON
 error:&error];
 if (user == nil) {
 return [RACSignal error:error];
 } else {
 return [RACSignal return:user];
 }} }];
 }}

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- (RACSignal *)fetchMeUser
 return [[self.client getPath:@"/me"] flattenMap:^(id JSON) { NSError *error; SPUser *user = [SPUser userWithJSON:JSON
 error:&error];
 if (user == nil) {
 return [RACSignal error:error];
 } else {
 return [RACSignal return:user];
 }} }];
 }}

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- (RACSignal *)fetchMeUser
 return [[self.client getPath:@"/me"] flattenMap:^(id JSON) { NSError *error; SPUser *user = [SPUser userWithJSON:JSON
 error:&error];
 if (user == nil) {
 return [RACSignal error:error];
 } else {
 return [RACSignal return:user];
 }} }];
 }}

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- (RACSignal *)fetchMeUser
 return [[self.client getPath:@"/me"] flattenMap:^(id JSON) { NSError *error; SPUser *user = [SPUser userWithJSON:JSON
 error:&error];
 if (user == nil) {
 return [RACSignal error:error];
 } else {
 return [RACSignal return:user];
 }} }];
 }}

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- (RACSignal *)fetchMeUser
 return [[self.client getPath:@"/me"] flattenMap:^(id JSON) { NSError *error; SPUser *user = [SPUser userWithJSON:JSON
 error:&error];
 if (user == nil) {
 return [RACSignal error:error];
 } else {
 return [RACSignal return:user];
 }} }];
 }} check out Mantle!


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- (RACSignal *)fetchMeUser
 return [[self.client getPath:@"/me"] flattenMap:^(id JSON) { NSError *error; SPUser *user = [SPUser userWithJSON:JSON
 error:&error];
 if (user == nil) {
 return [RACSignal error:error];
 } else {
 return [RACSignal return:user];
 }} }];
 }}

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- (RACSignal *)fetchMeUser
 return [[self.client getPath:@"/me"] flattenMap:^(id JSON) { NSError *error; SPUser *user = [SPUser userWithJSON:JSON
 error:&error];
 if (user == nil) {
 return [RACSignal error:error];
 } else {
 return [RACSignal return:user];
 }} }];
 }}

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3. Putting it together

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[[[[client logIn] then:^{ return [client fetchMeUser]; }] flattenMap:^(SPUser *me) { return [client fetchNewslettersForUser:me]; }] subscribeNext:^(NSArray *files) { NSLog(@"Files: %@", files); }}
 error:^(NSError *error) { // Handle error }];

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[[[[client logIn] then:^{ return [client fetchMeUser]; }] flattenMap:^(SPUser *me) { return [client fetchNewslettersForUser:me]; }] subscribeNext:^(NSArray *files) { NSLog(@"Files: %@", files); }}
 error:^(NSError *error) { // Handle error }];

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[[[[client logIn] then:^{ return [client fetchMeUser]; }] flattenMap:^(SPUser *me) { return [client fetchNewslettersForUser:me]; }] subscribeNext:^(NSArray *files) { NSLog(@"Files: %@", files); }}
 error:^(NSError *error) { // Handle error }];

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[[[[client logIn] then:^{ return [client fetchMeUser]; }] flattenMap:^(SPUser *me) { return [client fetchNewslettersForUser:me]; }] subscribeNext:^(NSArray *files) { NSLog(@"Files: %@", files); }}
 error:^(NSError *error) { // Handle error }];

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[[[[client logIn] then:^{ return [client fetchMeUser]; }] flattenMap:^(SPUser *me) { return [client fetchNewslettersForUser:me]; }] subscribeNext:^(NSArray *files) { NSLog(@"Files: %@", files); }}
 error:^(NSError *error) { // Handle error }];

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[[[[client logIn] then:^{ return [client fetchMeUser]; }] flattenMap:^(SPUser *me) { return [client fetchNewslettersForUser:me]; }] subscribeNext:^(NSArray *files) { NSLog(@"Files: %@", files); }}
 error:^(NSError *error) { // Handle error }];

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UI&IO

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UI+IO

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Newsletter Your name Your email address Sign Up Sign Up Brooklyn 4:00 PM 100%

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Your name Your email address Sign Up validate Newsletter

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Your name Your email address Sign Up validate Newsletter

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oh boy

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oh boy, why me?

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 
 
 ]] 
 
 
 
 self.name.rac_textSignal,
 self.email.rac_textSignal reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"];
 return @(at.location != NSNotFound &&
 name.length > 0);
 }];

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 
 
 ]] 
 
 
 
 self.name.rac_textSignal,
 self.email.rac_textSignal reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"];
 return @(at.location != NSNotFound &&
 name.length > 0);
 }];

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 
 
 ]] 
 
 
 
 validName,
 validEmail reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"];
 return @(at.location != NSNotFound &&
 name.length > 0);
 }];

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 
 
 ]] 
 
 
 
 validName,
 validEmail reduce:^(NSString *name, NSString *email) {
 NSRange at = [email rangeOfString:@"@"];
 return @(at.location != NSNotFound &&
 name.length > 0);
 }];

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RAC(self.signUpButton, enabled) = [RACSignal
 combineLatest:@[
 
 
 ]] 
 
 
 
 validName,
 validEmail reduce:^(NSNumber *name, NSNumber *email) {
 return @(name.boolValue && email.boolValue);
 }]; }];
 


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RAC(self.signUpButton, enabled) = [RACSignal combineLatest: 
 
 
 
 validName, validEmail reduce:^(NSNumber *name, NSNumber *email) { RACSignal *validName = [self.name.rac_textSignal map:^(NSString *name) { return @(name.length > 0); }];
 
 switchToLatest];
 


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RACSignal *validName = [self.name.rac_textSignal map:^(NSString *name) { return }] 
 RACSignal *validEmail = [[self.email.rac_textSignal map:^(NSString *email) { return [[client validateEmail:email] startWith:@NO]; }] switchToLatest];
 


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RACSignal *validName = [self.name.rac_textSignal map:^(NSString *name) { return }] 
 RACSignal *validEmail = [[self.email.rac_textSignal map:^(NSString *email) { return [[client validateEmail:email] startWith:@NO]; }] switchToLatest];
 


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RACSignal *validName = [self.name.rac_textSignal map:^(NSString *name) { return }] 
 RACSignal *validEmail = [[self.email.rac_textSignal map:^(NSString *email) { return [[client validateEmail:email] startWith:@NO]; }] switchToLatest];
 


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Your name Your email address Sign Up validate Newsletter

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Newsletter Your name Your email address Sign Up Brooklyn 4:00 PM 100%

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Newsletter Your email address Sign Up robb Brooklyn 4:00 PM 100%

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Newsletter Sign Up robb [email protected] Brooklyn 4:00 PM 100%

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Newsletter Sign Up robb Sign Up [email protected] Brooklyn 4:00 PM 100%

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Recap

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+ Declarative code Recap

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+ Declarative code + Easy handling of asynchronous tasks Recap

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+ Declarative code + Easy handling of asynchronous tasks + Great Composition Recap

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+ Declarative code + Easy handling of asynchronous tasks + Great Composition − Conceptual overhead Recap

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+ Declarative code + Easy handling of asynchronous tasks + Great Composition − Conceptual overhead − Debugging can get tricky Recap

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+ Declarative code + Easy handling of asynchronous tasks + Great Composition − Conceptual overhead − Debugging can get tricky Recap (dtrace support)

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Qs?

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Thanks!

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iPhone 5 Sketch Template
 courtesy of
 Denis Rojčyk ! Cloud icon
 curtesy of Dmitry Baranovskiy, from The Noun Project