Where to put reusable functions in IOS Swift?

Question

New to IOS programming but just wondering where is the best place to put functions that I would use throughout my code. For example, I want to write a few functions to perfo

Answer 1

For reusable functions it depends what I decide to use. For this specific case I use a separate file, because posting to a backend will become more complicated when the application evolves. In my app I use a backend class, with all kinds of helper classes:

struct BackendError {
    var message : String
}

struct SuccessCall {
    var json : JSON

    var containsError : Bool {
        if let error = json["error"].string {
            return true
        }
        else {
            return false
        }

    }
}

typealias FailureBlock  = (BackendError) -> Void
typealias SuccessBlock  = (SuccessCall) -> Void

typealias AlamoFireRequest = (path: String, method: Alamofire.Method, data: [String:String]) -> Request
typealias GetFunction = (path: String , data: [String : String], failureBlock: FailureBlock, successBlock: SuccessBlock) -> Void

class Backend {
   func getRequestToBackend (token: String )(path: String , data: [String : String], failureBlock: FailureBlock, successBlock: 

}

For other cases I often use extensions on Swift classes. Like for getting a random element from an Array.

extension Array {
    func sampleItem() -> T {
        let index = Int(arc4random_uniform(UInt32(self.count)))
        return self[index]
    }
}