Swift 4 and the Data API

Document created by Brian Hamm on Jul 11, 2018Last modified by Brian Hamm on Oct 14, 2018
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Update: October 13, 2018

This document, and some other Swift-related stuff, now resides at GitHub for anyone who wants to nerd out.

GitHub - starsite/SwiftFM: A service class for Swift to work with the FileMaker Data API


Update: September 9, 2018

After spending a couple months developing for the Data API, I've decided to update this document with more practical examples. The purpose of my original post was to quickly demo a basic Swift call to the Data API. These new examples show how to check status for an existing token, how to refresh expired tokens, and to make sure you're passing active tokens in your requests, where possible. Fetching a new session token for every request is lazy. Don't be that guy.


During testing, you can hardcode `baseURL` and `auth` values as below, but best practice is to keep sensitive info (such as API keys, etc.) outside of `Bundle.main`. It's safer to fetch that information from elsewhere and park it in `UserDefaults`. I fetch most of my environment settings from CloudKit, in `didFinishLaunching` or `didEnterForeground`. Doing it that way also provides a remote access kill-switch, if necessary.


1. Class vars and lets. A `let` is a constant, in Swift.

import UIKit


class ViewController: UIViewController {


//  let baseURL = UserDefaults.standard.string(forKey: "fm-db-path")   // better

//  let auth    = UserDefaults.standard.string(forKey: "fm-auth")      // better


    let baseURL = URL(string: "https: //<hostName>/fmi/data/v1/databases/<databaseName>")!

    let auth    = "xxxxxxxabcdefg1234567"  // base64 "user:pass"


    var token   = UserDefaults.standard.string(forKey: "fm-token")

    var expiry  = UserDefaults.standard.object(forKey: "fm-token-expiry") as? Date ?? Date(timeIntervalSince1970: 0)


    // ... (cont'd)




2. Bool check to see if there's an existing token in `UserDefaults`, and whether or not it's expired. The _ means we aren't using (don't care about) the token value right now, we only care that there /is/ one.

    // active token?

    func isActiveToken() -> Bool {

        if let _ = self.token, self.expiry > Date() {

            return true

        } else {

            return false






3. Refresh an expired token. The @escaping marker allows the `token` and `expiry` types to be passed sometime later (they're permitted to "escape" or "outlive" the function). That's typical for async calls in Swift. We'll call this function later, in `viewDidLoad()`

    // refresh token

    func refreshToken(for auth: String, completion: @escaping (String, Date) -> Void) {


        let url = baseURL.appendingPathComponent("/sessions")

        let expiry = Date(timeIntervalSinceNow: 900)   // 15 minutes


        // request

        var request = URLRequest(url: url)

        request.httpMethod = "POST"

        request.setValue("Basic \(auth)", forHTTPHeaderField: "Authorization")

        request.setValue("application/json", forHTTPHeaderField: "Content-Type")


        // task

        URLSession.shared.dataTask(with: request) { data, _, error in


            guard   let data  = data, error == nil,

                    let json  = try? JSONSerialization.jsonObject(with: data) as! [String: Any],

                    let resp  = json["response"] as? [String: Any],

                    let token = resp["token"] as? String

            else {

                    print("refresh token sad")




            // prefs

            UserDefaults.standard.set(token, forKey: "fm-token")

            UserDefaults.standard.set(expiry, forKey: "fm-token-expiry")


            completion(token, expiry)   // out^







4. This example shows an "or" request. Set your payload from a `UITextField` (or hardcode a query, like this) and pass it as a parameter.

    // query

    var payload = ["query": [   // or ->[[p1],[p2]]   and ->[[p1,p2]]

        ["bandName": "Daniel Markham"],

        ["bandName": "Sudie"]




    /// data api find request

    func findRequest(with token: String, layout: String, payload: [String: Any]) {


        let url = baseURL.appendingPathComponent("/layouts/\(layout)/_find")


        // serialize             

        guard let body = try? JSONSerialization.data(withJSONObject: payload) else { return }


        // request

        var request = URLRequest(url: url)

        request.httpMethod = "POST"

        request.addValue("Bearer \(token)", forHTTPHeaderField: "Authorization")

        request.addValue("application/json", forHTTPHeaderField: "Content-Type")

        request.httpBody = body


        // task

        URLSession.shared.dataTask(with: request) { data, _, error in


            guard   let data = data, error == nil,

                    let json = try? JSONSerialization.jsonObject(with: data) as! [String: Any]

            else {

                    print("api request sad")




            print("\n\(json)")   // disco!







5. In `viewDidLoad()`, check for an active token and hand it to our find request. If the token is missing/expired, we'll fetch a new one and pass `newToken` instead.


If you're new to Swift, `viewDidLoad()` is called only when stepping *into* a view. It is *not* called when navigating backward/down the stack. If you need to call a function every time the user enters a view, that's done in `viewWillAppear()` or `viewDidAppear()`.

    // did load

    override func viewDidLoad() {



        // apiRequest

        switch isActiveToken() {   

        case true:

            print("active token - expiry: \(self.expiry)")

            findRequest(with: self.token!, layout: "Bands", payload: self.payload)


        case false:

            refreshToken(for: auth, completion: { newToken, newExpiry in    // async

                print("new token - expiry: \(newExpiry)")

                self.findRequest(with: newToken, layout: "Bands", payload: self.payload)



        // ....


    // .did load


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