xcode - How to prevent a Command Line Tool from exiting before asynchronous operation completes

Question

In a swift 2 command line tool (main.swift), I have the following:

import Foundation
print("yay")

var request = HTTPTask()
request.GET("http://www.stackoverflow.com", parameters: nil, completionHandler: {(response: HTTPResponse) in
    if let err = response.error {
        print("error: (err.localizedDescription)")
        return //also notify app of failure as needed
    }
    if let data = response.responseObject as? NSData {
        let str = NSString(data: data, encoding: NSUTF8StringEncoding)
        print("response: (str)") //prints the HTML of the page
    }
})

The console shows 'yay' and then exits (Program ended with exit code: 0), seemingly without ever waiting for the request to complete. How would I prevent this from happening?

The code is using swiftHTTP

I think I might need an NSRunLoop but there is no swift example

question from:https://stackoverflow.com/questions/31944011/how-to-prevent-a-command-line-tool-from-exiting-before-asynchronous-operation-co

Answer 1

I realize this is an old question, but here is the solution I ended on. Using DispatchGroup.

let dispatchGroup = DispatchGroup()

for someItem in items {
    dispatchGroup.enter()
    doSomeAsyncWork(item: someItem) {
        dispatchGroup.leave()
    }
}

dispatchGroup.notify(queue: DispatchQueue.main) {
    exit(EXIT_SUCCESS)
}
dispatchMain()