Synchronous http request in Swift

sync-http.swift

import Foundation

func query(address: String) -> String {
    let url = URL(string: address)
    let semaphore = DispatchSemaphore(value: 0)
    
    var result: String = ""
    
    let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
        result = String(data: data!, encoding: String.Encoding.utf8)!
        semaphore.signal()
    }
    
    task.resume()
    semaphore.wait()
    return result
}

let preference = query(address: "http://the-rock-paper-scissors.herokuapp.com/newgame")
print("Computer preference: \(preference)")

NSLock will be better here

NSLock will be better here

How? @impul

@eonil ,

import Foundation

func query(address: String) -> String {
    let url = URL(string: address)
    let lock = NSLock()
    
    var result: String = ""
    
    let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
        result = String(data: data!, encoding: String.Encoding.utf8)!
        lock.unlock()
    }
    
    task.resume()
    lock.lock()
    return result
}

let preference = query(address: "http://the-rock-paper-scissors.herokuapp.com/newgame")
print("Computer preference: \(preference)")

@impul Are you sure that code work? It seems query function exits before result getting set.

NSLock is better because we have only one thread.

Can only be better if it actually worked.
Original works, NSLock version exits straightaway as pointed out by @eonil

The NSLock class uses POSIX threads to implement its locking behavior. When sending an unlock message to an NSLock object, you must be sure that message is sent from the same thread that sent the initial lock message. Unlocking a lock from a different thread can result in undefined behavior. https://developer.apple.com/documentation/foundation/nslock