UITextFieldDelegate textFieldShouldReturn with ReactiveCocoa - ios

Question

I am trying to implement UITextFieldDelegate textFieldShouldReturn handling with ReactiveCocoa. Unfortunately the subscribeNext block is run when I subscribe for the signal.
The implementation using delegation would be:
- (void)viewDidLoad
{
...
self.myTextField.delegate = self;
}
...
- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
if (textField == self.myTextField) {
NSLog(#"Let's go!");
}
return YES;
}
In ReactiveCocoa I have added a category for UITextField in a similar fashion like UITextView+RACSignalSupport.
#implementation UITextField (RACKeyboardSupport)
static void RACUseDelegateProxy(UITextField *self)
{
if (self.delegate == self.rac_delegateProxy) return;
self.rac_delegateProxy.rac_proxiedDelegate = self.delegate;
self.delegate = (id)self.rac_delegateProxy;
}
- (RACDelegateProxy *)rac_delegateProxy
{
RACDelegateProxy *proxy = objc_getAssociatedObject(self, _cmd);
if (proxy == nil) {
proxy = [[RACDelegateProxy alloc] initWithProtocol:#protocol(UITextFieldDelegate)];
objc_setAssociatedObject(self, _cmd, proxy, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
return proxy;
}
- (RACSignal *)rac_keyboardReturnSignal
{
#weakify(self);
RACSignal *signal = [[[[RACSignal
defer:^{
#strongify(self);
return [RACSignal return:RACTuplePack(self)];
}]
concat:[self.rac_delegateProxy signalForSelector:#selector(textFieldShouldReturn:)]]
takeUntil:self.rac_willDeallocSignal]
setNameWithFormat:#"%# -rac_keyboardReturnSignal", [self rac_description]];
RACUseDelegateProxy(self);
return signal;
}
#end
Here subscribeNext block is executed even if the Return Key was never pressed:
- (void)viewDidLoad
{
...
[self.myTextField.rac_keyboardReturnSignal subscribeNext:^(id x) {
Log(#"Let's go with RAC!");
}];
}
I have to use skip:1 to avoid that problem:
- (void)viewDidLoad
{
...
[[self.myTextField.rac_keyboardReturnSignal skip:1] subscribeNext:^(id x) {
Log(#"Let's go with RAC!");
}];
}
Any idea why this happens?
Solution:
- (RACSignal *)rac_keyboardReturnSignal
{
RACSignal *signal = [[[self.rac_delegateProxy
signalForSelector:#selector(textFieldShouldReturn:)]
takeUntil:self.rac_willDeallocSignal]
setNameWithFormat:#"%# -rac_keyboardReturnSignal", [self rac_description]];
RACUseDelegateProxy(self);
return signal;
}

Answer 1

You are returning a signal that immediately returns a value in your defer block, then concat-ing new values onto the stream when textFieldShouldReturn is invoked.
The code in UITextView+RACSignalSupport.m is calling reduceEach in order to return a string value that is extracted from the UITextView instance. The defer is used to merely have an initial value generated upon subscription.
Basically, I don't think you want the defer at all for your use case.