Playing with iOS MapKit Part 4: Race Conditions, Other Bugs, Wrap-up

Playing With MapKit

Part 1 MapKit Tutorials 

Part 2 Reverse Geocoding and Custom Annotation Callouts

Part 3 Making it Pretty

Part 4 Race Conditions, Other Bugs, and Wrap-up

As the functionality and the look was coming into place, I took note of bugs that I saw.

The most insidious bugs are ones that don’t happen all the time or under conditions (ex. when internet is especially slow or the computer is especially fast). One example is the race condition.

What is a Race Condition?

A race condition is a situation when the sequence of asynchronous responses results in an undesired effect.

My Example

Very quickly after starting the app, I was tapping the current location dot and I was seeing “Current Location” in the bubble. It should have said the address that the address was closest to. If I waited a couple seconds to tap the current location, it would display the address as expected.

This led me to believe that I had a race condition.

Under normal conditions:

  1. The map updates the user location calling its delegate mapView:didUpdateUserLocation: which starts the reverseGeocoding call based on the user’s location.
  2. The reverseGeocoding response is received and the completion block sets the annotation’s title with the address of the user location.
  3. When the user location dot is tapped, it will display a custom bubble using the annotation’s title in the label.

Usually the internet is fast enough that the reverseGeocoding response returns before the user location dot is tapped.

The two things that are racing are

  1. the reverseGeocoding network call and
  2. the tap of the current location dot.

If 1 finished first, then the app would work as intended. If 2 finished first, the experience would be suboptimal.

Design Choice

One way to fix this is to update the label when the reverseGeocoding network call came back.

At the end of the completion block, I added a method call to updatePinCallout, which pretends that the user location dot was tapped again and reloads the address.

- (void)updatePinCallout
  if (self.userLocationPin.selected) {
   [[NSOperationQueue mainQueue] addOperationWithBlock:^{
    [self.userLocationPin setSelected:YES animated:YES];

Just remember to use the mainQueue to retap the dot or else the address won’t update on screen.

This change also fixed another bug that happened when the user location would jump when WIFI was enabled and the address label would not update to the new address.

Alternative Choice

Another thing that I found solved the problem pretty well was to zoom the map to the user location immediately, so that the animation didn’t even give a chance to tap the user location dot.

Other Bugs

Writing code for multiple scenarios unnecessarily

When I first implemented zooming to fit destinations, I only zoomed when the location was outside of the visible region. I realized that sometimes this would not be sufficient because sometimes the map would be zoomed way out, so I decided to account for that scenario too. I would zoom in if the destination was in the original visible area. This got complicated quickly.

Eventually, I realized that it was too much and just made it always zoom to the destination. The code went from 14 lines to 1.

Simpler is Better

Testing Days Later

I thought I was done with the project. Wrong. A few days later, I was trying out the app on the bus and came across two bugs.

  1. I was on a bus and the location was updating very quickly and constantly centering the map on the new location. The problem was that I wanted to look around the map and couldn’t do that without it changing while I was using it.
    • This is easily fixed by only zooming on the time the map loads.
  2. I was looking for a Pret A Manger. When I saw the results page, I found it utterly useless because all of them said the same thing and I couldn’t tell which location was where.
    • I think it would have been cool to add some directions as to how far each location was from my current location and in which direction or add the cross streets.

As the Pragmatic Programmer said:

“Test your software, or your users will.”

Where to next?

There’s certainly a lot of ways this can go. Add friends, add Facebook integration, add Yelp results, use Google Maps. That would be fun to do, but would lack direction.

For a product to be real, it must have a real use.

The way that this app fits into my life has something to do with lunch (ergo the name LunchTime). In an effort to build good habits, one of them is to walk 10K steps a day. As I’ve discovered, this means walking 1.3 hours a day. If I don’t plan to walk, I won’t get near 10K.

So over lunch, I like to walk 10 to 15 minutes away and back. I think it would be cool to draw a diamond around your current location to see how far you can walk in 5 and 15 minutes and show how far each location is.

Options abound. Looking forward to the next expedition.

It’s been fun working with MapKit. Time to play around with something else. Who knows? I might be looking at WatchKit, EventKit, or something else entirely.

Playing with iOS MapKit Part 2: Reverse Geocoding and Custom Annotation Callouts

Playing With MapKit

Part 1 MapKit Tutorials 

Part 2 Reverse Geocoding and Custom Annotation Callouts

Part 3 Making it Pretty

Part 4 Race Conditions, Other Bugs, and Wrap-up

After following the tutorials in part 1, I wanted to keep exploring MapKit. As reverse geocoding was my next topic, I wanted to show the address of the current location in a callout (view that pops up above the pin).

To do this, I’ll need:

  1. A way to know when the current location was tapped
  2. A way to know the address of the current location
  3. A way to display the address in a callout

1. How do I know when the current location is tapped?

MKMapViewDelegate has a method called:

- (MKAnnotationView *) mapView:(MKMapView *)mapView 

that is called when an annotation is tapped.

How do I tell that this annotation is my current location?

Notice that the annotation is any class that conforms to MKAnnotation.

Current location comes in a special class called MKUserLocation so you just need to test if the annotation is that class.

if ([annotation isKindOfClass:[MKUserLocation class]]
) {

Within this if statement, I need to turn the currentLocation into an address.

This MKUserLocation has a CLLocation property, a BOOL property for whether it’s updating, a CLHeading property, a title and a subtitle.

2. How do I find the address with coordinates? (Reverse Geocoding)

Apple provides a CLGeocoder class that has the method

- (void)reverseGeocodeLocation:(CLLocation *)location 

All you need is the location which comes from MKUserLocation’s location property.

What does the completion handler return?

NSArray *placemarks, NSError *error

placemarks is an NSArray of CLPlacemarks. Each placemark has an addressDictionary. The key @”FormattedAddressLines” returns an array of formatted address lines.

Typically, there are three lines. One for address, another for city, state, and zip code, and one more for the country. In some situations, there are four lines where the first is the name of a venue.

3. How do I display the address?

One way is to set the callout for the annotation is to set the title of the annotation to the text you want in the callout. For example:

self.address = [NSString stringWithFormat:@" %@\n %@\n 
%@", street, cityState, country];
[(MKUserLocation *)annotation setTitle:self.address];

When I do this, the problem is that there is only one line and the rest of the address gets cut off.

Cut Off Callout

Adding line breaks to the title did not make it appear on additional lines, but only displayed the first line instead.

Callout title with line breaks

Messing with the left and right accessory buttons did not help either.

Callout with left and right accessory views colored red and blue
Callout with left and right accessory views colored red and blue

With no way to set more than two lines of text, I had to make a custom MKPinAnnotationView.

How do I make a custom annotation callout?

Since the callout is a property of the MKPinAnnotationView, I had to make a subclass of the MKPinAnnotationView and overwrite the setSelected: animated method.

- (void) setSelected:(BOOL)selected animated:(BOOL)animated
  1. Draw a label
  2. Set the text of the label with the annotation’s title
  3. Place a view as a subview of the MKPinAnnotationView subclass (which I called MultilineAnnotationView)
  4. Add the label as a subview of view.
Why MKPinAnnotationView and not the default user location view?

The default user location view is a class that you cannot access or subclass.

Custom Callout View
The custom callout works! (but not perfectly)

Up next, making things look pretty.

Playing with iOS MapKit Part 1: MapKit Tutorials

Playing With MapKit

Part 1 MapKit Tutorials

Part 2 Reverse Geocoding and Custom Annotation Callouts

Part 3 Making it Pretty

Part 4 Race Conditions, Other Bugs, and Wrap-up

A main difference between a smartphone and any other phone is that smart phones can tell you where they are. What does location tell you? Location provides context about what you are doing, where you’re going, and by extension, who you are.

Apple makes it easy to show this information on a map with MapKit.

At the Flatiron School, I got a good foundation for learning frameworks, but hadn’t worked with MapKit yet. Since it felt core to many mobile apps, I decided to explore it.

Demo Video

Here is a demo of the finished app. All the code is on Github.

First Stop on the MapKit Train: Tutorials

Whenever I get into a new framework, I learn best by jumping right in and  doing it. Tutorials are a great way to get started. They help me focus by limiting scope and stay productive before my natural curiosity wants to go down some rabbit holes. I also don’t want to reinvent the wheel.

If I have seen further it is by standing on the shoulders of giants.

-Isaac Newton

Searching for iOS Mapkit tutorial, I find some by Ray Wenderlich, TechTopia, and AppCoda. All three have been really useful in the past. I went with the TechTopia one because it was written about iOS 7.

Tutorial 1: Make a MKMapView and Show the Current Location


  • Add the MapKit framework
  • Make a MKMapView with Storyboards and import MKMapView
  • Assign the MKMapViewDelegate to the view controller
  • Set the MKMapView to show the current Location
  • *Not In Tutorial: Asking for Permission to Access User Location
  • *Set the location in Simulator
  • Zoom in on the MKMapView by changing the region
  • Change the MKMapView type
  • Update the MKMapView using the MKMapViewDelegate methods

*Most of this is already well explained in the tutorial. I want to point out two bumps on the road.

1. Simulator does not have a GPS, so you have to set the location by the menu bar: Debug -> Location -> Custom Location.

Google maps will give you latitude and longitude for any location if you click on the map. If it’s an icon, right click and click “What’s here?”.

Note: Sometimes the location doesn’t show up in the simulator the first time I run it. When I run it on another sized simulator, it works. Don’t know why this is.

2. More importantly, iOS 8 requires that you get permission to use the user location.

How to Get the Current Location Authorization Status

    CLAuthorizationStatus status = [CLLocationManager 

CLAuthorizationStatus is an enum of

  • kCLAuthorizationStatusNotDetermined = 0
  • kCLAuthorizationStatusRestricted = 1
  • kCLAuthorizationStatusDenied = 2
  • kCLAuthorizationStatusAuthorized = 3 (Deprecated iOS 8)
  • kCLAuthorizationStatusAuthorizedAlways = kCLAuthorizationStatusAuthorized = 4
  • kCLAuthorizationStatusAuthorizedWhenInUse = 5

Statuses start out as kCLAuthorizationStatusNotDetermined

How to Ask the User for Location Authorization

If you want current location data only when the customer is using the app:

[self.locationManager requestWhenInUseAuthorization];

If you want current location data even when the customer is not using the app:

[self.locationManager requestAlwaysAuthorization];

Here I have my CLLocationManager as a property of the class. Change self.locationManager to the name of your locationManager.

How to Add Properties to your Info.plist

Even though you think you’ve requested authorization, you are likely still missing one more piece.

Properties List

In the Supporting Files Folder of your app directory, there is a Info.plist file.

It’s a properties list that your app uses through out the app.

You have to have a property in there for NSLocationWhenInUseUsageDescription (or NSLocationAlwaysUsageDescription depending on which permission your asking for), which tells the customer why you are asking for their location information.

Permission Popup

How to tell if you received location authorization

There is a delegate method for the location manager that tell you when the authorization status changes.

- (void)locationManager:(CLLocationManager *)manager 

The status here is the CLAuthorizationStatus.

Remember to set the locationManager’s delegate to the class that implements the delegate method. In this case, I’ve set the delegate to self inside my view controller.

self.locationManager = [[CLLocationManager alloc] init];
self.locationManager.delegate = self;

Tutorial 2: Add Local Search with MKLocalSearchRequest and Display Results as MKPointAnnotation


  • Add a textField so the user can input search terms
  • Add an IB action for the textFieldReturn to call the performSearch method
  • Add a performSearch method that sends a MKLocalSearchRequest and handles the MKLocalSearchResponse by parsing its array of MKMapItems into MKPointAnnotations

This was pretty straight forward. Apple makes the searches super easy by giving you completion handlers.

How to Perform a Local Search

You just need a MKLocalSearch object and a MKLocalSearchRequest object.

MKLocalSearch *search = [[MKLocalSearch alloc] 

and call

- (void)startWithCompletionHandler: 

Tutorial 3: Find Directions with MKDirectionsRequest and Draw Them on the Map


  • Add a ResultsTableViewController to show the names and phone numbers of the venues
  • Add a RouteViewController to show the route to the destination
  • Set up a MKDirectionsRequest with a source and destination in the RouteViewController
  • Make a MKDirections instance that calculates directions
  • Pass the MKDirectionsResponse to a showRoute method that adds an overlay of the polylines of the MKRoutes in the response to the map
  • Set up how the overlay will look


The tutorial sets up a custom UITableViewCell, but that’s not really necessary because you can set the title as the name and the subtitle to the phoneNumber.

Why am I in the middle of the ocean?

It’s important that you implement the MKMapView delegate method

- (void)mapView:(MKMapView *)mapView didUpdateUserLocation:
(MKUserLocation *)userLocation

Otherwise, you’ll find yourself in the ocean next to West Africa a lot (that’s what happens when your coordinates are (0,0)).

How to Get Directions

Make an instance of MKDirections and call:

- (void)calculateDirectionsWithCompletionHandler:

Up next: Going beyond the tutorials

A Trip to the Met

Surrounded in a sea of options, I felt an urge to head to the Met.

Software development is art

On the way there, I tried to explain this urge. It became readily apparent as I walked through the halls of Egyptian wing that software development is as much an art as these. One can only hope to be in a museum some day. Though, any dreams that my software creations will outlast me may be overly optimistic.

Art requires repetition and experimentation

Looking at the Madame Cezanne exhibit, with it’s many renditions of the same lady, I am reminded that many versions were made before the final product was complete. This is an inherent part of the process of experimentation and exploration. Bad art has to be made before they can be judged bad and discarded to made room for good. This exhibit was only just a peek. Many shitty drafts were made that will never be on seen except by the artist.

Artists are judged on the height of their greatest accomplishment, not the first thing they make

Another thought that occurred to me was that people are judged on their greatest contributions or indiscretions. People only care at all about the early work when your best work has already been accepted as great. In the hindsight of a career, only highlights make it and most first moves are necessary to build the foundations of a great career. It’s really only by building a lot that one builds great things.

Let’s delay no further. Let’s get started.

Flatiron School Week 11 – Week in Review

Week 3 of Client Project

One of our teammates have been dealing with an emergency for most of the last two weeks, so we’re down to three people.

The Science Fair is Wednesday and we want to have something to showable, so we scoped down our project to just what needed to be shown.

From Monday to Tuesday, our team and our app really came together. We are in the performing stage of the team “form, storm, norm, perform” process. I’m glad that my investment of time paid off. Everyone pulled their own weight.

I’m really impressed why what we were able to do in 2 weeks. People were really impressed at the Science Fair.

I’ve been so focused that I haven’t really been paying attention to how the other client projects were going. It looks like they had bigger clients and bigger expectations. That’s the benefit of having a younger client.

We ended the week with a huge celebration over at Sammy’s. So much fun.

Flatiron School Week 10 – Week In Review

Week 2 of Client Projects

Notes to Self

This week felt like I was reliving my first year out of college when I was working as a paralegal/project manager in a client facing team. That year, I learned more about communication and relationship building than anything else, themes that came up this week.

  • Giving feedback is one of the most difficult conversations between people. Admitting that you’re wrong is another. All difficult conversations are best done promptly.
  • On a small team, having a team member that isn’t able to contribute at the same level is a productivity killer because it means that productive people need to stop and invest in that team member. (Sam Altman has more on this topic)
  • Communication is key. When communication breaks down, trust erodes and people assume the worst.
  • As much as possible, it’s good to talk directly with the people involved. You build trust this way.
  • Don’t hesitate to pick up the phone.
  • Teams should have a single point of contact when working with clients to provide updates.

Flatiron School Week 9 – Conquering Fear of Complex CocoaPods

For my Flatiron School Presents project, a classmate and I worked on a chat app.

For the chat user interface, I wanted it to look like Apple’s Messages app. There was a perfect CocoaPod for this: JSQMessagesViewController. After reading the Getting Started section, I still had no clue how to bridge the gap between my existing app and this UI. It was overwhelming and I was very discouraged.

9 Steps to Overcoming Fear of Complex CocoaPods

Step 1: Recognizing the problem

I knew that I was avoiding it. I looked for another CocoaPod but they weren’t quite the same. I even thought of building my own chat UI. I realized that I needed to be able to use CocoaPods though, so there was no getting around it.

Step 2: Read Zen Pencils

In need of inspiration, I turned to the Zen Pencils. I have the book too, which makes for very motivating reading.

Step 3: Go to sleep

It was 9 already and so I figured it was better to get some sleep than try that night.

Step 4: Try a simpler CocoaPod.

I hadn’t used enough CocoaPods up to this point, so I tried a smaller one. I looked at HPL chat. It had a tenth as many classes as JSQ did and I went for it. It didn’t work, but got me started.

Step 5: Look at the demo

The challenge of open source software is that there’s not always good documentation. It doesn’t cost money, but it costs time to read and understand how to use the code.

Fortunately, I saw that JSQ had a demo and downloaded it. Playing around with the demo really helped me understand how the pieces related to each other.

Step 6: Start customizing the demo

I didn’t need images or videos so, I got rid of the accessory button on the toolbar. I had to get familiar with the documentation to find which parts I needed to change. Once I removed the button, I felt much more confident about adapting the demo.

Step 7: Move the demo to a new project and make it work

Now I tried to make the demo fit my purpose, removing as much as I could to reduce it to the elements I needed. Here was a sandbox that I could use to unit test the functionality before I put it into my app and get everything tangled up.

Step 8. Add to the app

With the chat working on it’s own, I had to hook it up to my project. By this point, I realized that I just needed to make a couple  subclasses of the classes that the CocoaPod needed and replace my existing messages class with those.

Step 9. Fear Conquered

After I was done, I read the CocoaPod’s Getting Started again and now it all makes sense. Going through implementing this pod has been a process of gradual building of exposure, comfort and confidence with CocoaPods. I’m really happy that I did this. Fear of technology really comes down to not understanding how it works.

Flatiron School Week 9 – Resolving my first real git merge conflict

This week we started our client projects. 19 people broke down into teams of 4 or 5. There were four clients and our team had four people. This was the first time that I really needed to deal with git merge conflicts and develop a workflow.

It wasn’t long before I had a conflict.

There were three files that I conflicts with:

  1. AppDelegate.m
  2. the .pbxproj file
  3. a xccheckout file

1. AppDelegate.m

I knew how to resolve the first one, but as I tried to do that, my file directory on the left side of Xcode disappeared. It was time to ask for help. Zach, one of our TAs, helped me put together a plan to resolve the conflicts.

I had to back out of the merge, so I used

git merge --abort

and then reset the head to the last commit because there some uncommit changes that I didn’t want anymore.

git reset --hard <commit id>

2. the .pbxproj file

Apparently that file directory is stored in the .pbxproj file. The way that we resolved this was by telling git to just join the two versions together in the .gitattributes file by adding:

*.pbxproj merge=union

Another way to resolve this is to choose one version of the pbxproj.

git checkout --ours <directory/file>

Replace “ours” with “theirs” to get the version being merged into the current branch.

I had to add in some files that were no longer referenced by the pbxproj file after the merge using this second method.

3. a xccheckout file

For the .xccheckout file, this was a file that should have been ignored. I added this to the .gitignore file.


The problem was that both versions that I was trying to merge still had this file in tracked files. I had to remove this file from both repos by running:

git rm --cached <directory/file>

Once the .xccheckout file was removed, I could merge the two repos.

Both the .gitignore and .gitattributes files should be set up at the beginning of a project.


Since that week, we’ve had to resolve conflicts many times. Following Github’s workflow has been pretty useful. I’ve found that the best way to resolve conflicts is prevention. We designed our workflow so that each person worked on a different part of the app and that minimized conflicts.

Flatiron School Week 8 – Week in Review

Topics: ScrollViews, views without storyboard, xibs/nibs, NSOperationQueue

This week was the last week of lecture, so we covered a grab bag of advanced topics.

Notes to Self

ScrollViews are sexy.

Bad public speakers (an anti-pattern)
  • don’t bring the audience with them and just start talking. Don’t explicitly say what questions they will address and how those are relevant to the audience.
    • Shouldn’t be thinking “what are we talking about?” “why are we talking about this?”
  • don’t speak loud enough.
  • don’t provide context for what they are saying and what problems they are trying to solve
  • go way too deep into things that the audience neither has context for or cares about
  • don’t paint a picture

Flatiron School Week 7 – Week in Review

Topics: APIs + Core Data, Authentication, Multithreading

Mistakes and Lessons

Symptom: API calls don’t tell you a lot when they don’t work. I wasn’t getting anything out of an internet request. Debugging API calls can feel like a text based adventure.

Mistake: Errors in strings are hard to debug. Apparently, when I had made the url, there was an extra “%”.

Lesson: Copy and paste urls that work from Postman, or use an encoder to convert strings to urls.

Symptom: When I changed the colors in my bocce game, the logic for choosing the next team to go broke.

Mistake: I had changed my colors away from the default colors (e.x. blueColor) to RGB values and had used == to compare the objects. The correct way to compare the objects is using an isEqual. Turns out that when you use [UIColor colorName] using == to compare is ok because they are at the same memory location.

Lesson: Use isEqual with objects and == with primitives.

Notes to Self

There are some times when I just have to slow down and plan out how something works. I was making a tableView that updated an API and a Core Data store. This very quickly got too complicated to keep in memory and I had to write down the interactions step by stem.

My partner and I decided to divide and conquer a lab. It became very hard for me to test along the way, because I was dependent on his piece to make mine work.

“If You Want To Go Fast, Go Alone. If You Want To Go Far, Go Together”