NSNotification + KeyboardNotifications

NSNotification+KeyboardNotifications.h

#import <UIKit/UIKit.h>

@interface NSNotification (KeyboardNotifications)

- (NSTimeInterval)keyboardAnimationDuration;
- (UIViewAnimationCurve)keyboardAnimationCurve;
- (CGRect)keyboardFrame;

- (void)animateSynchronouslyWithKeyboard:(void(^)(void))animation completion:(void(^)(void))completion;

@end

NSNotification+KeyboardNotifications.m

#import "NSNotification+KeyboardNotifications.h"

@implementation NSNotification (KeyboardNotifications)

- (NSTimeInterval)keyboardAnimationDuration
{
    NSAssert([self.name isEqualToString:UIKeyboardWillShowNotification] ||
             [self.name isEqualToString:UIKeyboardWillHideNotification], nil);

    return [self.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
}

- (UIViewAnimationCurve)keyboardAnimationCurve
{
    NSAssert([self.name isEqualToString:UIKeyboardWillShowNotification] ||
             [self.name isEqualToString:UIKeyboardWillHideNotification], nil);
    
    UIViewAnimationCurve curve;
    [[self.userInfo valueForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&curve];
    return curve;
}

- (CGRect)keyboardFrame
{
    NSAssert([self.name isEqualToString:UIKeyboardWillShowNotification] ||
             [self.name isEqualToString:UIKeyboardWillHideNotification], nil);

    return [self.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
}

- (void)animateSynchronouslyWithKeyboard:(void(^)(void))animation completion:(void(^)(void))completion
{
    NSParameterAssert(animation);
    
    [UIView beginAnimations:nil context:(__bridge_retained void *)[completion copy]];
    [UIView setAnimationDuration:[self keyboardAnimationDuration]];
    [UIView setAnimationCurve:[self keyboardAnimationCurve]];
    
    if (completion) {
        [UIView setAnimationDelegate:self];
        [UIView setAnimationDidStopSelector:@selector(keyboardAnimationDidStop:finished:context:)];
    }
    
    animation();
    
    [UIView commitAnimations];
}

- (void)keyboardAnimationDidStop:(NSString *)animationID
                        finished:(NSNumber *)finished
                         context:(void *)context
{
    if (context) {
        void(^completion)(void) = (__bridge_transfer void(^)(void))context;
        completion();
    }
}

@end