Archive for the ‘iOS’ Category.

Migrating AFNetworking to NSURLSession

I have some legacy Objective-C code that I want to bring up to the latest iOS code. Part of this is migrating AFNetworking to NSURLSession.

Not that I have anything against AFNetworking of course, I have used it for a very long time, especially when the communications capabilities in the Foundation framework were a bit more primitive than they are now. I have just been trying to reduce dependencies in my projects where I can, and for my communications needs, the newer Foundation classes give me the same kind of ease of use that AFNetworking has.

For example, here is a simple example of some of the legacy code that I have in the app:

NSURL *url = [NSURL URLWithString:@""];    
AFHTTPRequestOperation *op = [[AFHTTPRequestOperation alloc] initWithRequest:[NSURLRequest requestWithURL:url]];
[op setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    // do something with the operation.responseString
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    // an error occurred
[op start];

And here is what it looks like when you migrate to NSURLSessionDataTask:

NSURL *url = [NSURL URLWithString:@""];
NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    dispatch_async(dispatch_get_main_queue(), ^{
        if (error != nil)
            // an error occurred
            // do something with the data
[task resume];

All in all, I think that 7 years of usage (I migrated to AFNetworking in 2013 as described in the post Migrating ASIHTTPRequest to AFNetworking) is pretty good for using a library. Kudos to the team maintaining that library, I do not know if I would have the patience to stick with it for that long.

BTW, Happy Birthday to John Myung, bass player for Dream Theater.

App crashes on iOS Simulator without debugging

If your app in the iOS Simulator works when debugging with Xcode, but the very same app crashes if you try to launch it without debugging, check your app for a framework listed under Linked Frameworks and Libraries, but not listed under Embedded Binaries. Once the framework shows up in both places, deploy the app again by debugging with Xcode, and then stop the debugging and try to launch it again on the Simulator.

BTW, Happy Birthday to Randall Munroe, creator of the xkcd web comic.

Swift app crashes with dyld Library not loaded message

So you are humming along on your new Swift app, and all of a sudden, when you bring in a framework revision or try to deploy to a device, you suddenly start getting dyld: Library not loaded messages when the app tries to launch.

Most likely, the reason for this is that the setting for embedding the Swift standard libraries is turned off, and the app for some reason needs them. The fix is easy enough, just go into your build settings for your app and look for “Always Embed Standard Swift Libraries”. Turn this setting on for your app’s target, clean, and then try to run again.

BTW, Happy 20th Anniversary to the iMac, which was announced to the world by former Apple CEO Steve Jobs on this date in 1998. I have had a few iMacs through the years, and they are great machines.

Background thread URL download in Swift 4

I was recently working on a project in swift, and was not able to quickly find a way to use a background thread to do a URL download in Swift 4. There were plenty of snippets and tutorials out there, but they were all for older versions of Swift. (BTW Swift, you have to stop it with these breaking changes.)

So here is what I cobbled together to download from the OpenAQ web site, which has an open API to provide air quality data.

The Swift class that does the downloading and processing of the data from the site is this class, which I called OpenAQ.swift:

//  OpenAQ.swift
//  openaq
//  Created by Brian Prescott on 11/16/17.
//  Copyright © 2017 Brian Prescott. All rights reserved.
import UIKit
class OpenAQResult: NSObject {
    var city: String = ""
    var count: Int = 0
    var country: String = ""
    var locations: Int = 0
protocol OpenAQDelegate: class {
    func didFinish(sender: Any)
    func didError(sender: Any)
class OpenAQ: NSObject {
    weak var delegate:OpenAQDelegate?
    var returnValue: [OpenAQResult] = []
    func readDataBackground() -> Void {
        let urlString = ""
        guard let url = URL(string: urlString) else { return }
        URLSession.shared.dataTask(with: url) { (data, res, err) in
            guard let data = data else {
            do {
                let json = try JSONSerialization.jsonObject(with: data, options: []) as! [String: Any]
                let resultsArray = json["results"] as! NSArray
                var retval: [OpenAQResult] = []
                for x in resultsArray {
                    let dict = x as! NSDictionary
                    let res = OpenAQResult()
           = dict.value(forKey: "city") as! String
                    res.count = dict.value(forKey: "count") as! Int
           = dict.value(forKey: "country") as! String
                    res.locations = dict.value(forKey: "locations") as! Int
                    if (res.count >= 10000) {
                self.returnValue = retval.sorted(by: { $0.count > $1.count })
                self.delegate?.didFinish(sender: self)
            } catch {
                print("An error occurred")

So then to use this class, here is a template of what your main view controller (or wherever you want to use it) would look like:

class MasterViewController: UITableViewController {
    var detailViewController: DetailViewController? = nil
    var objects = [OpenAQResult]()
    var openAQ: OpenAQ? = nil
    override func viewDidLoad() {
        openAQ = OpenAQ()
        openAQ?.delegate = self
        // do the rest of your initialization
    // the rest of your class would go here
extension MasterViewController: OpenAQDelegate {
    func didError(sender: Any) {
        print ("An error occurred!!!")
    func didFinish(sender: Any) {
        objects = (sender as! OpenAQ).returnValue
        if (objects.count == 0) {
            let alert = UIAlertController(title: "Error", message: "The data could not be loaded. Please establish an internet connection and press the Refresh button above.", preferredStyle: UIAlertControllerStyle.alert)
            alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
            self.present(alert, animated: true, completion: nil)
        DispatchQueue.main.async {
            // do something here
            // for example, reload a table view

In the code above, when the didFinish method is called, the objects instance variable is retrieved from the openAQ variable, and you can then do something with the data you just retrieved.

BTW, Happy Thanksgiving to all my U.S. readers. It has been a very trying year personally and all around, but we still have so much to be thankful for.

Watch out for #ifdef TARGET_IPHONE_SIMULATOR

I just wanted to take a moment before the sands of time in the April hourglass run out for a friendly reminder for those iOS developers who are working in older Objective-C code bases. Watch out for #ifdef TARGET_IPHONE_SIMULATOR, as at some point, a newer version of the iOS SDK broke this check. In the current TargetConditionals.h file, TARGET_IPHONE_SIMULATOR resolves to either a 0 or a 1 (eventually, see below), which means that no matter where you run the code, TARGET_IPHONE_SIMULATOR will be defined, hence the code inside the #ifdef will always run.

The solution is of course to use the following line instead:


Keep in mind that TARGET_IPHONE_SIMULATOR itself is marked as deprecated in the iOS 10 SDK TargetConditionals.h file, so I suppose to be future-proof, you should instead use:


BTW, Happy Honesty Day to my U.S. readers. All you need to know about Honesty Day is that I think it is one of the best days on the calendar.

Find the bundle ID of an app in the App Store

Have you ever had to find the bundle ID of an app in the App Store? Well if you have, there does not seem to be a direct way to do it, so here is how I found the information.

First, use the iTunes Link Maker to search for iOS apps, find the app you need to discover the bundle ID for, and click on it. This will pull up a screen with an embed code link, find the numeric ID code.

Then, visit this URL, replacing the X’s with the numeric ID you just found:

After you plug in your numeric ID, the Apple site should spit back a JSON file in response, look for the bundleId entry.

BTW, I am a day late, but Happy 40th Anniversary to Slap Shot, one of the finest cinematic masterpieces of all time.

Eliminate noise from the iOS Simulator console

If you find that you are getting a lot more stuff showing up on the console when debugging your app in the Simulator, you are not alone. Luckily, there is a way to eliminate noise from the iOS Simulator console output.

To do this, go into the scheme editor for your target, select the Run Debug option on the left, select the Arguments tab on the right, and under Environment Variables, click the + button to add a new one called OS_ACTIVITY_MODE, and set its value to false.

BTW, a posthumous Happy Birthday to the King, Elvis Presley.

Ignore warnings in a specific file in Xcode

If you use any 3rd party or open source code in your iOS or macOS application, you know how deflating it is to get your code all compiling with no errors or warnings, only to have your open source code spit out lots of warnings. If only there were a way to ignore warnings in a specific file in Xcode…

Well as it turns out, you can go into the Build Phases section in your target’s settings, find the file or files you want to disable warnings for, double click on the Compiler Flags, and add in the following entry:

-w -Xanalyzer -analyzer-disable-all-checks

This entry will have the additional benefit of also disabling the Clang static code analysis warning messages for the files, which can be just as annoying as the warnings.

BTW, Happy 60th Birthday to the Wizard, Jordan Rudess of Dream Theater. Jennifer and I saw them here in Columbus tonight as they performed The Astonishing live, and the show was great.


I have a lot more projects that I am working on at my new gig, and as such, I am always looking for my METHOD_LOG definition. It is a quick define that I put in my Objective-C code so that I can log what class and method I am in, without having to type out a description of the class and method into an NSLog statement.

So here is the code for METHOD_LOG, along with a DebugLog define that I use quite often instead of NSLog:

#if defined(DEBUG)
    #define METHOD_LOG (NSLog(@"METHOD_LOG: %@ %s", NSStringFromSelector(_cmd), __FILE__))
    #define DebugLog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__)
    #define METHOD_LOG
    #define DebugLog(...)

BTW, Happy International Caps Lock Day.

Codesign error: “Warning: –resource-rules has been deprecated in Mac OS X >= 10.10”

So you are humming along and everything is going great. Then all of a sudden you start getting the error message “Warning: –resource-rules has been deprecated in Mac OS X >= 10.10”, especially if you are using some kind of tool to re-sign code.

Apparently, in your build settings for your target in Xcode, there is a Code Signing Resource Rules Path entry that is no longer supported. Once this is removed and the app is rebuilt, the message should no longer appear. Of course, if you are re-signing an app that you do not have the source code for, this could be a challenge.

Here is the technical note from Apple that describes the issue:


BTW, Happy 60th Birthday to the best rock guitar player of all time, Joe Satriani. I am looking forward to seeing Joe in a few weeks at the G4 Experience on Long Island.