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Kill process running on port

Frequently I’ll run into the case where my IDE (Intellij, Xcode/Vapor) will fail and leave a web server running on a port. I can’t start it again because it is already running. The only way to proceed is to restart your computer or find and kill the process.

To find the a process running on a port you can use the lsof command. You can filter with “-i”, which lists IP sockets.

$ lsof -i tcp:8080

The command will produce output like:

COMMAND  PID   USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
Run     8299 ddiego   15u  IPv6 0xb2782dc730d0c751      0t0  TCP localhost:http-alt (LISTEN)

The PID is the process identification number. You can pass this to the kill command to kill the process:

$ kill -9 8299
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U.S. Zip Code Validation in Swift

Here is a small function that will validate a US Zip Code using a Regexp with a: NSPredicate in Swift.

func validate(input: String?) -> Bool {
    guard let input = input else { return false }

    return NSPredicate(format: "SELF MATCHES %@", "^\\d{5}(?:[-\\s]?\\d{4})?$")
        .evaluate(with: input.uppercased())
}

Playground: zip-code-validation-playground

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Charles Proxy on iOS Simulator

Charles “is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic between their machine and the Internet. This includes requests, responses and the HTTP headers (which contain the cookies and caching information).”

It is one of my favorite tools for debugging network applications. It supports Mac, Windows, Linux and even iOS.

The instructions on their website for SSL connections from within iPhone applications are not quite complete. Especially the last step which is tricky and I often forget. Here are complete instructions for SSL proxy connections on the iOS Simulator.

1. Add SSL Location. After launching Charles, open the menu:
Proxy > SSL Proxying Settings

The click the “Add Button”

Charles - Add Domain

Type in the location you want to add. You can use wildcards if you like. When you’re done, you should see you location in the list:

Charles - SSL Proxying Settings

2. Install Charles Root Certificate in iOS Simulators. Open the menu:

Help > Install Charles Root Certificate in iOS Simulators

Charles - Install Root Cert iOS

This will install the Charles Root Certificate on the Simulator.

3. Enable the Root Certificate. This is the step, they forget to document. And the last part of it is tricky.

On the Simulator, go to:

Settings > General > About > Certificate Trust Settings

Charles - iOS Trust Settings

Swipe the switch to enable the certificate. It will give a warning which you must choose “Continue”

Charles - iOS Trust Settings Enable

You’ll be placed back on the Certificate Trust Settings page with the switch on:

Charles - iOS Trust Settings Enabled

Now is the critical part. Quit the Simulator. Now run your application again and Charles will be able to decrypt your network communications.

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Covert GPX to Strava Route

Strava has a labs feature to convert a GPX file to a route: Strava GPX to Route.

But it doesn’t work for me:
Strava GPX to Route Error

And I’m not the only one:
Error computing Route when loading a GPX file

Here is a workaround for converting a GPX file to Strava Route:

1. Export the GPX file.

2. Go to GPSies and import your GPX file:

GPSies Import

Verify it:

GPSies Verify

It adds a timing of 10 mph. You can change this, but it doesn’t matter.

3. Export the GPX Track file.

GPSies Export

4. Go Strava and Upload Activity.

Strava Upload

Click Choose File and select the GPX file exported from GPSies. This will create a new ride.

5. Save the activity as a route.

Strava Create Route

Strava Route Verify

Strava Name Route

6. Delete the activity.

Strava Delete

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iOS Swipe Keyboard to dismiss

In iOS 7, Apple added an option to UIScrollView which could allow you to dismiss the keyboard when dragged.

UIScrollViewKeyboardDismissMode

public enum UIScrollViewKeyboardDismissMode : Int {

    case none

    case onDrag // dismisses the keyboard when a drag begins

    case interactive // the keyboard follows the dragging touch off screen, and may be pulled upward again to cancel the dismiss
}

This is very easy to do. Just set the keyboardDismissMode property to .onDrag or interactive:

let tableView = UITableView(frame: .zero, style: .plain)
tableView.keyboardDismissMode = .interactive

You should set this on all tableviews that contain text fields.

For example code, see: https://github.com/dougdiego/iOSDemos

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Vapor Error – root manifest not found

I got this error when trying to build a Vapor project.

$ vapor build
No .build folder, fetch may take a while...
Fetching Dependencies [ • ]
Error: backgroundExecute(code: 1, error: "warning: \'fetch\' command is deprecated; use \'resolve\' instead\nerror: root manifest not found\n", output: "")

I recently experienced a lot of error with getting Vapor 3.0 to run during the beta and Swift 4.1. I assumed the error had to do with that. Had I read closer I might have figured it out. I was not in the build directory. Duh! After changing to the build directory everything worked fine.

If you end up on this page, make sure you are in the build directory when trying to build a Vapor project.

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Programmatically selecting a row in a UITableView

I had a need to programmatically select a row in a UITableView. In order to do this, you have to do two things:

 
let indexPath = IndexPath(row: 0, section: 0)
self.tableView.selectRow(at: indexPath, animated: true, scrollPosition: .none)
self.tableView.delegate?.tableView!(self.tableView, didSelectRowAt: indexPath)

selectRow highlights the selected row and didSelectRowAt will call didSelectRowAt if you need to perform whatever action you defined.

For example code, see: https://github.com/dougdiego/iOSDemos

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macOS Word Breaks

macOS has a feature that lets you change the word delimiter.  By default it considers the “.” to be part of the word and selects the whole thing.  But you can change it to break on the period.

This feature used to be called “Word Break” in previous macOS release.  In macOS Sierra it can be found by going to “System Preferences” and selecting “Language & Region”.  Here you’ll see an option for “Region”.  If you’re in the United States, it should be set to “United States”.  You can change it to “United States (Computer)”.

Here’s what’s happening: ASCII special characters that are part of words between alphabetic ASCII characters:

  • '.:_ in Standard
  • '_ in English (United States, Computer)

 

Here is an example of “United States”

 

 

Here is an example of “United States (Computer)”

 

 

If you change the word break setting, you have to quit and reopen applications to apply the changes.

Note: I found this tip a few years ago and used it on my Mac. After getting a new Mac, it took me awhile to figure out how to do this again. This post is a reminder to myself for next time I need to remember how to do this.

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Fastlane solution for Crashlytics – Missing dSYMs

While working on a new Xcode project, I was unable to get my crash logs on Crashlytics . In the Crashlytics dashboard, I would see the following error:

"Found 1 unsymbolicated crash from missing dSYMs in 1 version in the last 24 hours"

Crashlytics even had a page dedicated to this: All about Missing dSYMs.

In my case the issue was with bitcode being enabled, which it is by default on all new iOS Projects. When bitcode is enabled, Apple recompiles your project on their server. Then you need to download the dSYMS to your computer and upload them to Crashlytics. This is a manual process that takes a lot of time. I was dreading doing this a second time after figuring out the process.

I figured this is something that fastlane might be able to help me with. Sure enough, they’ve come up with a lane to automate this. You can read more about it here:

Automatically download and upload dSYM symbolication files from iTunes Connect for Bitcode iOS apps using fastlane

Simply add this to your Fastfile:

lane :refresh_dsyms do
  download_dsyms                  # Download dSYM files from iTC
  upload_symbols_to_crashlytics   # Upload them to Crashlytics
  clean_build_artifacts           # Delete the local dSYM files
end

Then run it like this:

fastlane refresh_dsyms

Thanks fastlane!

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DispatchGroup with Swift

Sometimes you have a need to wait on several asynchronous tasks before doing something in your code. DispatchGroup is a powerful API that lets you group together these tasks into one task.

DispatchGroup allows for aggregate synchronization of work. You can use them to submit multiple different work items and track when they all complete, even though they might run on different queues. This behavior can be helpful when progress can’t be made until all of the specified tasks are complete.

For example you have a ViewController that shows data from three different APIs. You need data from all 3 API’s before you can render the page. One way to do this would be to chain network calls and render the page after the 3rd API completed. But this leads to ugly nest code and requires that the APIs be called synchronously, rather than asynchronously.

Let’s looks look at how to solve this problem by chaining first.

I’ll be using httpbin.org for these examples. It’s a great tool for testing HTTP requests and responses.

This URL allows you to make an HTTP request that will wait a duration in seconds. For example, this will take 10 seconds to load:
https://httpbin.org/range/1024?duration=10

I’m using this API so you can easily see the time difference.

I wrote a simple method called makeNetworkRequest(), which take a duration in seconds and uses NSURLSession to call httpbin.org:

    func makeNetworkRequest(duration:Int, completion: @escaping (_ result: String?) -> Void) {
        let config = URLSessionConfiguration.default
        let session = URLSession(configuration: config)
        let url = URL(string: "https://httpbin.org/range/1024?duration=\(Int(duration))")!
        NSLog("makeNetworkRequest() \(url)")
        let task = session.dataTask(with: url) { (data, response, error) in
            if error != nil {
                NSLog(error!.localizedDescription)
                completion(nil)
            } else {
                if let str = String(data: data!, encoding: String.Encoding.utf8) {
                    completion(str)
                } else {
                    completion(nil)
                }

            }
        }
        task.resume()
    }

 

Here is an example using nesting:

makeNetworkRequest(duration: 2) { (str) in
	NSLog("Request #1 \(str ?? "nil"))\n")

	makeNetworkRequest(duration: 3) { (str) in
		NSLog("Request #2 \(str ?? "nil"))\n")

		makeNetworkRequest(duration: 10) { (str) in
			NSLog("Request #3 \(str ?? "nil"))\n")
			
			NSLog("Done!")
		}
	}
}

As you can see this accomplishes a solution to our problem, but there is a lot of nested code and called the API’s synchronously. It took 15 seconds to wait for all 3 responses.

Now let’s try this with DispatchGroup. With DistpatchGroup you first create a DistpachGroup:

let group = DispatchGroup()

For each block of code you want to execute you call:

group.enter()

Before the API and then

Group.leave()

When it finishes executing.

Finially group.notifiy(…) will be called when all group.enter() calls have a successful group.leave() response:

group.notify(queue: DispatchQueue.global(qos: .background)) {
NSLog(“All 3 network reqeusts completed”)
completion(strings)
}

Here’s a complete example:

func makeNetworkRequests(completion: @escaping (_ result: String?) -> Void) {
        let group = DispatchGroup()
        var strings = "start"
        
        group.enter()
        makeNetworkRequest(duration: 2) { (str) in
            NSLog("Request #1 \(str ?? "nil"))\n")
            if let str = str {
                strings = strings + str
            }
            group.leave()
        }
        
        group.enter()
        makeNetworkRequest(duration: 3) { (str) in
            NSLog("Request #2 \(str ?? "nil"))\n")
            if let str = str {
                strings = strings + str
            }
            group.leave()
        }
        
        group.enter()
        makeNetworkRequest(duration: 10) { (str) in
            NSLog("Request #3 \(str ?? "nil"))\n")
            if let str = str {
                strings = strings + str
            }
            group.leave()
        }
        
        group.notify(queue: DispatchQueue.global(qos: .background)) {
            NSLog("All 3 network reqeusts completed")
            completion(strings)
        }
    }

Notice how much easier this code is to read. No more nested blocks. It’s also asynchronous. It only takes 10 seconds for all 3 to return, because we’re only waiting on the longest API to respond.

For example code, see: https://github.com/dougdiego/iOSDemos

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