RACable(textView.text) vs. matchedTextView.rac_textSignal

gistfile1.m

@interface CAFMatchedTextViewController ()
@property (strong, nonatomic) IBOutlet UITextView *matchedTextView;
@end

@implementation CAFMatchedTextViewController {

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self.matchedTextView.rac_textSignal subscribeNext:^(NSString *string) {
        NSLog(@"via rac_textSignal '%@'", string);
    }];
    
    [RACAble(self.matchedTextView.text) subscribeNext:^(NSString *string) {
        NSLog(@"via RACAble '%@'", string);
    }];

    self.matchedTextView.text = @"asdf";
};

@end

gistfile2.txt

2013-04-07 20:31:00.823 MyApp[96042:c07] via rac_textSignal ''
2013-04-07 20:31:00.829 MyApp[96042:c07] via RACAble 'asdf'

I assumed that these would both log 'asdf', but I wonder why rac_textSignal isn’t.