Enabling an UIButton using Reactive Cocoa RACSignal

问题

I have a UIButton added to a view. My view also has three text box viz. username, password and confirmPassword. Based on the legitimate content of these text box, I need to enable my signUp button.

Here is my code snippet :-

    UIButton *signUp = [[UIButton alloc]initWithFrame:CGRectMake(10, 100, 50, 20)];
    signUp.backgroundColor = [UIColor greenColor];

    signUp.enabled = NO ;
    [self.view addSubview:signUp];

    RACSignal *formValid = [RACSignal
    combineLatest:@[
    username.rac_textSignal,
    password.rac_textSignal,
    confirmPassword.rac_textSignal
    ]
    reduce:^(NSString *username, NSString *password, NSString *passwordVerification)        {
    return @([username length] > 0 && [password length] > 8 && [password      isEqual:passwordVerification]);
    }];

    RAC(signUp.enabled) = formValid; //Error is here

In the last line, I'm getting two errors:-

1. Implicit conversion of 'BOOL' (aka 'signed char') to 'id' is disallowed with ARC
2. Expected identifier

I am new to Reactive Cocoa. Please ignore the mistakes.

回答1:

The RAC() macro takes two arguments at a minimum, the object that's the target and a valid keypath on that object.

Like so:

RAC(signUp, enabled) = formValid;

You're passing it signUp.enabled, which is a single item, and happens to be a BOOL, not an object. After the macro is expanded, the BOOL is passed to a method that expects an object argument, so the compiler complains:

[[RACSubscriptingAssignmentTrampoline alloc] initWithTarget:signUp.enabled nilValue:<#garbage#>][@keypath(signUp.enabled, nil)]

回答2:

Use RAC(signUp, enabled) instead of RAC(signUp.enabled). The RAC macro takes at least two arguments, the object and the keypath you are binding.

来源：https://stackoverflow.com/questions/20266886/enabling-an-uibutton-using-reactive-cocoa-racsignal