iOS helper class for discovering current keyboard frame

KeyboardHelper.h

#import <Foundation/Foundation.h>

@interface KeyboardHelper : NSObject

@property (nonatomic, readonly) CGRect keyboardBounds;

+ (KeyboardHelper *)instance;

@end

KeyboardHelper.m

#import "KeyboardHelper.h"

@implementation KeyboardHelper

+ (KeyboardHelper *)instance {
    static KeyboardHelper *_instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [[self alloc] init];
    });
    
    return _instance;
}

+ (void)load {
    [[NSNotificationCenter defaultCenter] addObserver:[self instance]
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    
    // Register notification when the keyboard will be hide
    [[NSNotificationCenter defaultCenter] addObserver:[self instance]
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
}

- (void)keyboardWillShow:(NSNotification *)notification {
    _keyboardBounds = [[notification.userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
}

- (void)keyboardWillHide:(NSNotification *)notification {
    _keyboardBounds = [[notification.userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
}