Can anyone help me to integrate RASA with iOS(swift) integration? I didn’t find any article for iOS.
Read this: Your Own Website
This is not specific for a website as the title says, it applies for anything that uses REST. Could be a website, an Android App, and iOS App, or even a smart microwave 
So as long as you can send the correct JSON format via REST as shown below (ref), and get the response, you can do it anywhere. It comes up to your Swift skills after that 
{
"sender": sender_id,
"message": user_message
}