Lock v2 for iOS allows you to specify additional fields that the user must complete before creating a new account. The extra fields will be shown after the basic fields (email, username, password).

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Adding custom fields

When signing up the default information requirements are the user’s email and password. You can expand your data capture requirements as needed. Capturing additional signup fields here will store them in the user_metadata, which you can read more about in Metadata. 
.withOptions {
  $0.customSignupFields = [
    CustomTextField(name: "first_name", placeholder: "First Name", icon: LazyImage(name: "ic_person", bundle: Lock.bundle)),
    CustomTextField(name: "last_name", placeholder: "Last Name", icon: LazyImage(name: "ic_person", bundle: Lock.bundle))
  ]
}
You must specify the icon to use with your custom text field. That’s it! If you have enabled users Sign Up in the Application’s Dashboard, after they complete the basic fields (email/username, password) and hit Submit, they will be prompted to fill the remaining fields. The user must fill all of the custom fields before being able to complete signup. When requesting a user Sign Up or Sign In, the extra fields will be attached to the user_metadata attribute in the request body. You can access them by querying the user profile at any time, even from the Dashboard in the User’s section.