This is a basic in-app keyboard. The same method could be used to make just about any keyboard layout. Here are the main things that need to be done:

• Create the keyboard layout in an .xib file, whose owner is a Swift or Objective-C class that is a UIView subclass.
• Tell the UITextField to use the custom keyboard.
• Use a delegate to communicate between the keyboard and the main view controller.

Create the .xib keyboard layout file

• In Xcode go to File > New > File… > iOS > User Interface > View to create the .xib file.
• I called mine Keyboard.xib
• Add the buttons that you need.
• Use auto layout constraints so that no matter what size the keyboard is, the buttons will resize accordingly.
• Set the File’s Owner (not the root view) to be the Keyboard class. This is a common source of error. You’ll create this class in the next step. See the note at the end.

Create the .swift UIView subclass keyboard file

• In Xcode go to File > New > File… > iOS > Source > Cocoa Touch Class to create the Swift or Objective-C class. Choose UIView as a superclass for newly created class
• I called mine Keyboard.swift (Keyboard class in Objective-C)
• Add the following code for Swift:

import UIKit

// The view controller will adopt this protocol (delegate)
// and thus must contain the keyWasTapped method
protocol KeyboardDelegate: class {
    func keyWasTapped(character: String)
}

class Keyboard: UIView {

    // This variable will be set as the view controller so that 
    // the keyboard can send messages to the view controller.
    weak var delegate: KeyboardDelegate?

    // MARK:- keyboard initialization

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        initializeSubviews()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        initializeSubviews()
    }

    func initializeSubviews() {
        let xibFileName = "Keyboard" // xib extention not included
        let view = NSBundle.mainBundle().loadNibNamed(xibFileName, owner: self, options: nil)[0] as! UIView
        self.addSubview(view)
        view.frame = self.bounds
    }

    // MARK:- Button actions from .xib file

    @IBAction func keyTapped(sender: UIButton) {
        // When a button is tapped, send that information to the 
        // delegate (ie, the view controller)
        self.delegate?.keyWasTapped(sender.titleLabel!.text!) // could alternatively send a tag value
    }

}

• Add the following code for Objective-C:

**Keyboard.h File**

 #import <UIKit/UIKit.h>

 // The view controller will adopt this protocol (delegate)
 // and thus must contain the keyWasTapped method
 @protocol KeyboardDelegate<NSObject>
 - (void)keyWasTapped:(NSString *)character;
 @end

 @interface Keyboard : UIView
 @property (nonatomic, weak) id<KeyboardDelegate> delegate;  
 @end

Keyboard.m File

#import "Keyboard.h"

@implementation Keyboard

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    [self initializeSubviews];
    return self;
}

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    [self initializeSubviews];
    return self;
}

- (void)initializeSubviews {
    NSString *xibFileName = @"Keyboard"; // xib extention not included
    UIView *view = [[[NSBundle mainBundle] loadNibNamed:xibFileName owner:self options:nil] firstObject];
    [self addSubview:view];
    view.frame = self.bounds;
}

// MARK:- Button actions from .xib file

-(IBAction)keyTapped:(UIButton *)sender {
    // When a button is tapped, send that information to the
    // delegate (ie, the view controller)
    [self.delegate keyWasTapped:sender.titleLabel.text]; // could alternatively send a tag value
}

@end