title: Password validation in UITextField in iOS 10 --> Objective C
body: <p>I'm having 1 UITextfield for password in my iPhone application.</p>
  
  <p>I want to validate this textfield with the following validation.</p>
  
  <p>Must be at least 6 characters</p>
  
  <p>Must contain at least one english letter, one digit and Remaining all</p>
  
  <p>special characters are make as optional (ie not mandetory)  </p>
  
  <p>how can I restrict the UITextField with above requirements. please anyone help me out to do this..</p>