How to read stream using Openai completion API in Swift - iOS? - swift

Question

I am trying to read the output in stream (as it comes) rather than waiting up for the whole response.
I have used the following code.
func caller() {
let completionAPIURL = URL(string: "https://api.openai.com/v1/completions")!
var request = URLRequest(url: completionAPIURL)
request.httpMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("<Token>", forHTTPHeaderField: "Authorization")
let requestBody = """
{
"model": "<model>",
"prompt": "<prompt>",
"max_tokens": 200,
"stream": true
}
"""
request.httpBody = requestBody.data(using: .utf8)
let task = URLSession.shared.dataTask(with: request) { data, response, error in
if let error = error {
print("Error: \(error)")
return
}
print((response as? HTTPURLResponse)?.statusCode)
guard let httpResponse = response as? HTTPURLResponse,
(200...299).contains(httpResponse.statusCode) else {
print("Error: invalid HTTP response code")
return
}
guard let data = data else {
print("Error: missing response data")
return
}
let eventStreamString = String(data: data, encoding: .utf8)!
let eventStreamLines = eventStreamString.components(separatedBy: "\n")
for event in eventStreamLines {
let eventFields = event.components(separatedBy: ":")
if eventFields.count < 2 {
continue
}
if fieldName == "data" {
if fieldValue == "[DONE]" {
// Stream terminated
break
} else {
// Process event data
print(event)
}
}
}
}
task.resume()
}
The problem is, it still waits till whole response is in place and then prints the data. What I am trying to achieve is to get the data as and how stream is generated, and not after the whole response is in place.
I am comparatively newbie and would expect a detailed help.