Swift Weekly – Issue 04 – The Swift Runtime (Part 3) – Operators

I have always been interested in finding out how different compilers work with basic operators such as +, -, % and so on. This week on the train I was thinking that it would be nice if somebody could explore how Swift deals with operators so, long story short, I decided to do it myself.

In this edition of Swift Weekly, I will show you how the Swift compiler works deals with (system and your own) operators and how to use operators to ensure you get the maximum performance.

Note: in this edition of Swift Weekly, I’m going to change things a little bit and instead of building for the debug configuration, I am going to build for Release to ensure that the assembly code that we are going to analyze is as optimized as what you will get when you release the app for the App Store. Optimization is hence enabled and the assembly output is long. That means setting the Optimization Level in your build settings to Fastest, Smallest [-Os] to ensure you get the export GCC_OPTIMIZATION_LEVEL=s export when you build your project.

Note: to ensure that the assembly code which we will look at is clean and nice without too much unnecessary code, I will remove bits and pieces of it but will keep all the assembly code that is relevant.

Continue reading this article on Swift Weekly’s home page here.

Swift Weekly – Issue 03 – The Swift Runtime (Part 2) – Enumerations

This is the second article in the Swift Runtime series of the Swift Weekly. In this article, we will dig deeper into the Swift Runtime and how the compiler deals with producing code for enumerations. Saturday morning writings are always fun! Let’s get this show started.

If you are an Objective-C or Swift programmer and have not done any Assembly programming or are simply not concerned with the low-level details of this article, jump right into the Conclusion section at the end to get the juice of this article.

Continue reading this Swift Weekly issue on Github.

Swift Weekly – Issue 02 – The Swift Runtime (Part 1)

In this edition, I wanted to write about arrays and dictionaires and take the easy route. But I thought to myself: wouldn’t be cool if _somebody_ dug deep into the Swift runtime for crying out loud? Then I thought that I cannot wait for somebody to do that so I’m going to have to do that myself. So here, this edition of Swift Weekly is about the Swift runtime. At least the basics.

Please note that I am using a disassembler + dSYM file. I am disassembling the contents of the AppDelegate with some basic code in it and then hooking my disassembler up with the dSYM file to see more details.

Also in this article I am testing the output disassembly of Xcode 6.1 on the x86_64 architecture, not ARM which is available on iOS devices.

Continue reading this article on Swift Weekly’s Github page: https://github.com/vandadnp/swift-weekly/tree/master/issue02

Swift Weekly – Issue 01 – Pointers

I have started working on a new project called Swift Weekly. The reasons behind this decision are plenty. I’ve noticed throughout years of publishing books that the best way to learn is to teach. In my quest to learn Swift better and better every day I have decided that I want to write about it. My son has recently been born so I am very busy at home too which means that I don’t have much time to write. So the weekly nature of Swift Weekly is perfect for me. Also, I believe in giving to the community so that is the third reason.

Swift Weekly issue 01 focuses on the niche subject of pointers in Swift. Swift Weekly is all hosted on GitHub and you can find it here:

Swift Weekly on GitHUb

Have a read through the first issue and see what you think. Ideas and suggestions are welcome. Also spread the word and share this with your Swift lover friends!

Building and Running Python Scripts with Xcode 6.1

Follow these steps:

1. Open Xcode
2. Create a new project and select Other from under the OS X category when the dialog appears, and then choose External Build System:
   

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3. In the next page, give your project a name “product name” and then in the “build tool”, choose the path of your Python interpreter. If you don’t know where your Python interpreter is, open Terminal and type in which python to get the path to the interpreter, like so:
   

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4. Then save your project on disk
5. From the Product menu, choose Scheme and then Edit Scheme or just Option-click the little Play button on top left of Xcode. Now you should see the Edit Scheme screen which looks like this:
   

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6. Now tap on the Info tab on top of the dialog and then press on the Executable combo-box (which currently says “None”) and then from the list, choose “other…”
   

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7. An open-dialog will appear waiting for you to select your build tool, again! This is a bug in Xcode. So press the Cmd+Shift+G button in the open-dialog and when the “Go to the folder” dialog appears, enter the path of your Python interpreter again like so:
   

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8. Once you are done, press the Go button and then press the Choose button
9. Back in the Edit Scheme dialog, uncheck the “Debug executable option as you don’t want Xcode to attach the LLDB debugger to Python. That’s not useful. This step is very important.
   
   

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10. Now tap on the Arguments tab and then under the “Arguments Passed on Launch”, press the + (plus) button and then type in “test.py” without the quotation marks, like so:
    

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11. Now tap on the Options tab and then under the “Working directory” section, tap the “Use custom working directory” and then tap on the little Folder button. Once the open-dialog appears, choose the root folder of your Xcode project:
    

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12. Now press the Close button to close the Edit Scheme dialog
13. Press the Cmd+N combination on keyboard or just select from the menus, File->New->File…
14. In the New file dialog, from the left hand side, choose OS X and then Other and then choose Empty and then press the Next button:
    

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15. Name your file “test.py” (without the quotation marks) and then ensure that you are saving it under your project’s main folder, the same folder that you set your “Working directory” to a few steps ago. Once you are done, press the Create button.
    

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16. Write a simple Python script in your “test.py” file like so:
    

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17. Now run your application and have a look at the console in Xcode to see your Python script successfully executed:
    

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That was it really. Good luck everyone. If you have any questions, just let me know.

Xcode 6.1, beta 2

I have now updated all example codes of O’Reilly’s iOS 8 Swift Programming Cookbook to be compatible with Xcode 6.1, Beta 2 and iOS 8.1. You can access all the sample codes on Github.

You can also get the video version of the book here.

iOS 8 Swift Programming Cookbook

Hi lovely readers 🙂

My iOS 8 book is out and it is ALLLLL new, rewritten to use Swift with tons of new stuff in it.

Check it out, it is 50% off. Click here to go to O’Reilly’s website to purchase the book.

Also a surprise, I have also done a video course to teach you all about iOS 8 programming with Swift. THAT too is 50% off for a limited time. You can click here to get the videos.

Happy coding everyone

Swift: Convert Unmanaged to String

Edit 1 (20th October 2014): Apple has now fixed this issue. To convert an unmanaged object to managed, just use the takeUnretainedValue() or the takeRetainedValue() method on it, based on whether you want to take a retained or unretained value.

So let’s say you have an Unmanaged<AnyObject> value that you know internally contains a value of type CFStringRef and you want to convert this to a value of type String in Swift. This is how I have managed to do that:

func convertCfTypeToString(cfValue: Unmanaged!) -> String?{

/* Coded by Vandad Nahavandipoor */

let value = Unmanaged.fromOpaque(
cfValue.toOpaque()).takeUnretainedValue() as CFStringRef
if CFGetTypeID(value) == CFStringGetTypeID(){
return value as String
} else {
return nil
}
}

Shown in Xcode it looks like this:

Creating string enumerations in Objective-C (The ultimate solution)

A while ago I wrote on my blog about a solution to one of the most common questions asked by Objective-C programmers which is “How can I create string enumerations?”. Well, the solution that I’ve given has immediately become one of the top subjects that attracts developers to my blog, as I can see in my stats. I thought I should now take it to a whole other level and get rid of the limitations that I had presented in the old solution, and come up with a fresh perspective.

The following video is the result of my work on this subject. I hope you’ll enjoy watching it.

Getting the most out of your WiFi dongle data plan (The definitive guide)

I am currently facing a situation where I need to carry out my work while I am connected to a WiFi dongle. I have spent about £20 for 6GB of data that can be used for up to 3 months, whichever comes first. So I have now learnt a lot of tricks on how to minimize my data usage and save money. Here, I want to share with you some of these tricks.

Trick 1 – Disabled images in your browser

If you view the web without images, your browser does not have to load those images from the internet so you will save A LOT of data. Every browser is different so I cannot tell you how to do that on every browser. Here is how to disable the loading of images on Safari on OS X:

1. Go to Safari Preferences
2. Go to the Advance tab
3. At the bottom of the Advance tab, find the “Show Develop menu in menu bar”
4. Then close the preferences window
5. Go to the newly-shown Develop menu and choose Disable Images

That’s it. Some websites will not look nice without images and that just shows you how some web developers have now become too reliant on using images! Their fault really.

Trick 2 – Use Git commands carefully

I use Git through the terminal and two of the most useful commands that I use quite often are git fetch and git rebase. Now, git fetch, will fetch every new branch and all change-sets from the server and brings it into your local machine. What you want to do is to replace git fetch with the following command:

git fetch origin NAME OF BRANCH

So if you are on a branch named “ios7” and you want to just bring the remote changes on that branch to your local repo, do this:

git fetch origin ios7

git rebase origin/ios7

Now you got only the changes in that branch and you rebased to the latest changes

Trick 3 – Use Adblock… A LOT

Install Adblock on your browser and go to your popular websites and start blocking anything that looks useless and will consume your data. So just start blocking all content that is irrelevant.

Trick 4 – Disable Flash

I don’t have to explain this. Flash videos are memory, CPU and data hungry. They consume your battery so fast it is unbelievable. Just disable Flash to make sure your browser will not try to load those darn Flash videos for you.

Trick 5 – Stop watching videos on websites

Do not go to YouTube and other streaming video websites. They are very data hungry no matter how low you have set the quality of the videos. Watch videos when you are on a proper broadband, not on a tiny WiFi dongle.

Trick 6 – Subscribe to websites with push notifications

I read MacRumors quite a lot. I go to their website probably 3-4 times a day. But instead of doing that, it’s best that you subscribe to push notifications from news websites that offer that service. Then you can get push messages directly to your OS X desktop of new content that get posted on those websites instead of going there every time you want to check the news. A push notification will only contain the new article, not the whole website. But if you go and browse the website, you are viewing everything that is on the front page at least, hopefully without the images, as one of the tricks you learnt earlier!

Trick 7 – Stop opening a browser page ever time you think you’ve lost your internet connection

We all do this. When we think we have no internet connection, which can happen on a daily commute on a Wifi dongle, we open our browsers and navigate to our favorite website. If the website loads, we go “Aha, it works”. Instead of that, do this:

1. Open Terminal
2. Type this: ping http://www.apple.com

Once you see ICMP packets going and coming back, you know at least ICMP is working and you are almost 99.99% sure that your internet works.

Trick 8 – Do not preload top hits in your browser

Users of Safari or most modern browsers know that when they type in the search field for anything, a few “suggested” websites and terms will appear automatically. For instance, if you start typing “blood”, in your search field in your browser, you may get suggested words such as “blood pressure”, “check your blood sugar level”, and etc. Every time you type something in your browser’s search field, your browser will hit your search engine and look for suggested words and links. This will take battery and will use your internet. To disable this in Safari, follow these steps:

1. Open Safari Preferences
2. Go to the Privacy tab
3. In the “Smart search field” area, click the “Prevent search engine from providing suggestions”
4. In the same area, click the “Do not preload Top Hit in the background”

Okay that is it for now. These are all the tricks I have up my sleeves for saving you some data usage on your WiFi dongle. If you have any other tips that you believe are worth sharing with others, please let me know and I will include them here.

Enjoy