Parsing JSON with Swift 4 JSONDecoder
Probably you saw many JSON parsing examples, but this one is really easy. And available out of the box with Swift 4.
All you have to do is create models from Codable superclass, and use:
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let decoder = JSONDecoder(); let myData = try! decoder.decode(MyModel.self, from: data!) |
Check out provided playground here!
Output in console should be:
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Colors: Color(color: "black", category: "hue", type: "primary") Color(color: "white", category: "value", type: "primary") Color(color: "red", category: "hue", type: "primary") Color(color: "blue", category: "hue", type: "primary") Color(color: "yellow", category: "hue", type: "primary") Color(color: "green", category: "hue", type: "secondary") |
TLSV1_ALERT_PROTOCOL_VERSION when trying to install python packages
If executing:
python setup.py install
give you error like:
[SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:645) -- Some packages may not be found!
it may be caused by outdate OpenSSL. But if after executing:
python -c "import ssl; print(ssl.OPENSSL_VERSION)"
you see something like:
OpenSSL 1.0.2n 7 Dec 2017
then your SSL is pretty good. What to do then?
1. If you are in Virtual Env mode, deactivate it
2. Remove your Virtual Env
3. Run “brew update”
4. Run “brew install openssl” just in case
5. Run “brew install python3”
Next thing is check available python versions which you can use in venv:
ls /Library/Frameworks/Python.framework/Versions/
If you will see only “3.5”, go to python.org and download newest MacOs package (currently 3.6.5) then install as usual.
After installing make you that:
ls /Library/Frameworks/Python.framework/Versions/
will show:
3.5 3.6
Now you can create new Virtual Env with forced python 3.6:
virtualenv envname --python=python3.6
Now installing packages should work.
How to enable php-intl extension for php 7.1 using XAMPP on MacOS High Sierra
This may seem trivial, but in fact about 2 months ago some clever guys made changes in brew repository, so doing just:
brew install php71-intl
will show you error with message that such recipe doesn’t exists. Also XAMPP comes without intl extension so is there any working solution which does not require full and manual php compilation?
Fortunately, there is. There is temporary fix in another brew repo, so all you have to do is:
brew tap kyslik/homebrew-php
brew install kyslik/php/php71-intl
And this works. Really. Enjoy.
How to get UIImage from OpenGL in Swift 3
As you probably notices, simple screen drawing is useless if it comes to OpenGL view. So is it possible to generate UIImage from such? Of course, lets suppose your custom drawing class extends UIView, then just add:
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func getSnapshot() -> UIImage? { let s = CGRect(x: 0.0, y: 0.0, width: self.bounds.width, height: self.bounds.height) let dataLength = Int(s.size.width * s.size.height * 4.0) let buffer: UnsafeMutableRawPointer? = malloc(dataLength) glReadPixels(0, 0, GLsizei(s.size.width), GLsizei(s.size.height), GLenum(GL_RGBA), GLenum(GL_UNSIGNED_BYTE), buffer); let pixelData: UnsafePointer = (UnsafeRawPointer(buffer)?.assumingMemoryBound(to: UInt8.self))! let cfdata: CFData = CFDataCreate(kCFAllocatorDefault, pixelData, dataLength * MemoryLayout<GLubyte>.size) let provider: CGDataProvider! = CGDataProvider(data: cfdata) let iref: CGImage? = CGImage(width: Int(s.size.width), height: Int(s.size.height), bitsPerComponent: 8, bitsPerPixel: 32, bytesPerRow: Int(s.size.width)*4, space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: CGBitmapInfo.byteOrder32Big, provider: provider, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent) UIGraphicsBeginImageContext(CGSize(width: CGFloat(s.size.width), height: CGFloat(s.size.height))) let cgcontext: CGContext? = UIGraphicsGetCurrentContext() cgcontext!.setBlendMode(CGBlendMode.copy) cgcontext!.draw(iref!, in: CGRect(x: CGFloat(0.0), y: CGFloat(0.0), width: CGFloat(s.size.width), height: CGFloat(s.size.height))) let image: UIImage? = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return image } |
This code works in XCode 9 and Swift 3.x.
OpenGL2: Very basic Swift3 example
As you guys probably notices, it was a while since last post here. I was quite busy with lot of projects, so did not had time for blogging. Continue reading
RxSwift: How to stream values with dynamic delay
Imagine such case – you have list of messages, each one with timestamp. And you want to show them in the same way they arrived, with same timings. How to achieve this with RxSwift?Continue reading
How to check object’s reference count in Swift 3?
Sooner or later, you will face the problem with object which are not deallocating. How to check if object gets deallocated? Just use deinit method like below:
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deinit { print("I'm deallocating \(self)") } |
If you won’t see such message when you think you class should be gone, the easiest way is to debug allocations. Because the most common reason for such behavior are strong references, you can print allocation counter this way:
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print("ARC count \(CFGetRetainCount(self))") |
But where to put this? First of all, in all you initialization methods. Just add some those prints after each few lines, and you should see where counter is growing. The same in cleanup methods, or if you dont have any, you can put this somewhere when your view controller is closing, like:
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self.dismiss(animated: false) { print("VC is closing \(self.myobject)") } |
And how to avoid strong references? The most common mistake, is using self in blocks, this is the place where you should use [unowned self], this way:
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Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: { [unowned self] (timer) in self.myobject.doSomething() }) |
How to use JSContext from JavaScriptCore to create two way communication with web page
What is “JavaScriptCore”? Well, it is a name for internal Safari javascript engine. Is it useful? For most of us it is not, but if you thinking about communicating between your Swift app and web page, it can be really useful.
Continue reading
Fatal error: unexpectedly found nil while unwrapping an Optional value
This can be really painful when you just started with Swift. It really happens very often and can be confusing. Where it comes from?Continue reading