How I can return value from async block in swift

Question

Please have a look into the code below:

backgroundthread.async {
    return self.mycallback() //return string, int etc
}

I want to return a

Answer 1

Your function would need a closure like so

func getAppConfigFromDB(_ key: String, completion: @escaping (String?) -> Void) {
    backgroundthread.async {
        completion("string here")
    }    
}

When you call your function you would do

getAppConfigFromDB("key") { (returnedString) in
    //returnedString is Optional("string here")
}