Add a button on right view of UItextfield in such way that, text should not overlap the button

use the rightView property of the UITextField. Basically, there are two properties (this one and leftView accordingly) that allow you to place custom views/controls inside the UITextField. You can control whether those views are shown or not by means of rightViewMode/leftViewMode properties:

textField.rightView = btnColor
textField.rightViewMode = .unlessEditing

for e.g

let button = UIButton(type: .custom)
button.setImage(UIImage(named: "send.png"), for: .normal)
button.imageEdgeInsets = UIEdgeInsetsMake(0, -16, 0, 0)
button.frame = CGRect(x: CGFloat(txt.frame.size.width - 25), y: CGFloat(5), width: CGFloat(25), height: CGFloat(25))
button.addTarget(self, action: #selector(self.refresh), for: .touchUpInside)
textField.rightView = button
textField.rightViewMode = .always

and call the action as

@IBAction func refresh(_ sender: Any) {
}