a function does internet fetching and return a value - swift

Question

I know the following piece of code is wrong, but I want to show my intent.
I want to write a method that will be called by multiple times. and this fetching method will tell me if it is successfully reached.
func fetch(url: String) -> Bool? {
let defaultSession = URLSession(configuration: URLSessionConfiguration.default)
let url = URL(string: url)
var bool: Bool? = nil
if let url = url {
defaultSession.dataTask(with: url, completionHandler: { data, response, error in
if let error = error {
print(error)
return
}
DispatchQueue.main.async {
if let httpResponse = response as? HTTPURLResponse, 200...299 ~= httpResponse.statusCode, let data = data {
// handle the data.
bool = true
} else {
print("something really wrong")
bool = false
}
}
}).resume()
}
return bool
}
if let bool = fetch(url: "https://www.google.com.hk/webhp?hl=en&sa=X&ved=0ahUKEwimubK7r-HVAhVFmZQKHazMAMMQPAgD"), bool == true {
// if it is true, I can go for next step.
}

Answer 1

Making the UI wait on completion of some API call is not recommended. The app will have no control over how long that API call will take. Situations with bad network connectivity can take several seconds to respond.
You can handle a situation like this is to use a completion handler.
func fetch(url: String, completion: #escaping (_ success: Bool) -> Void) {
let defaultSession = URLSession(configuration: URLSessionConfiguration.default)
let url = URL(string: url)
if let url = url {
defaultSession.dataTask(with: url, completionHandler: { data, response, error in
if let error = error {
print(error)
return
}
if let httpResponse = response as? HTTPURLResponse, 200...299 ~= httpResponse.statusCode, let data = data {
// handle the data.
completion(true)
} else {
print("something really wrong")
completion(false)
}
}).resume()
}
}
func testFetch () {
fetch(url: "https://www.google.com.hk/webhp?hl=en&sa=X&ved=0ahUKEwimubK7r-HVAhVFmZQKHazMAMMQPAgD") { (success) in
// if it is true, I can go for next step.
DispatchQueue.main.async {
if success {
// it was good
}
else {
// not good
}
}
}
}