Random Twists

Hi, my name is Daniel Skantze, I work as Head of Tech at Greatworks. I had lots of stuff I wanted to jot down and I didn't really know where so I started this page. As it turns out it has become more focused on code (primarily IOS, PHP, Wordpress, Javascript and Python) but you will also see stuff such as my flickr feed here. I am also into music production (fingertwister@soundcloud) as well photography (my photo blog here). var _gaq = _gaq || []; _gaq.push(['_setAccount', 'UA-25622010-1']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })();

[fingertwister]

I've written hundreds of Bash scripts over my career, but I still suck at Bash. I have to look up the syntax for simple logical structures every single time. If I want to do anything fancy with curl or sed, I have to go and look up man pages too. I spend hours brute forcing every possible combination of single and double quotes and escaping and double-escaping every character in my regular expressions until I get something that looks like abstract ASCII art, all while trying to remember the difference between grep and perl regular expressions.

Nice inspiration on how to write command line tools in nodejs

[fingertwister]

Unqiue conditions for CoreData

[fingertwister]

Tool to bulk download training data from Garmin Connect

I wrote my first Chrome Plugin. I use a Garmin FR 235 watch to track my runs. Through Garmin's apps each run is saved to Garmin Connect - their cloud platform. I use many apps to analyze my training data and I usually export activities as .tcx-files which is a general format for training data containing a sequence of GPS coordinates, heart rate data and some more.

It is possible to export to TCX from Garmin Connect but unfortunately it is only possible to export one activity at a time.

So there is where the chrome plugin comes into the picture. With it, you can select a bunch of activities and download them as a zip-file.

https://chrome.google.com/webstore/detail/garmin-activity-downloade/himhggflahpnjikoddlngaopcigalcjh

[fingertwister]

iOS Simulator  / CoreData - sqlite document folder

Pretty often I use Sqlite Manager for Firefox to check the CoreData sqlite files that I create in apps I build. It is quite a struggle to find out the document folder of the simulator apps since the path is pretty deep and there are some uuids involved.

So I wrote the following scripts to make this process a bit easier:

List the last 10 modified simulator sqlite files:

#!/bin/bash SIMULATOR_FOLDER=~/Library/Developer/CoreSimulator/Devices find $SIMULATOR_FOLDER -name "*.sqlite" -print0 | \ xargs -0 stat -f '%i -- %N' |\`` sort | \ grep Application | \ tail -n 10 | \ sed -e 's/[0123456789]* -- \(.*\)/\1/'

Copy the folder of the last modified sqlite file to the clipboard

#!/bin/bash SIMULATOR_FOLDER=~/Library/Developer/CoreSimulator/Devices \ LAST_FOLDER=$(find $SIMULATOR_FOLDER -name "*.sqlite" -print0 | \ xargs -0 stat -f '%i -- %N' | sort | grep Application | tail -n 1 | \ sed -e 's/[0123456789]* -- \(.*\)/\1/' | \ xargs -0 dirname) echo $LAST_FOLDER | pbcopy echo $LAST_FOLDER " was copied to clipboard"

[fingertwister]

Saving an iPod Shuffle

I recently found my old iPod Shuffle in a drawer. It came in very handy since I do a lot of running and I no longer use my iPhone to track my runs (the battery drain for a 1 hour+ run is just insane - can't take it anymore so I now use a Garmin watch instead).

But there was a minor issue... While the music on the iPod played fine iTunes refused to recognize it. It showed up in the device manager and all but no luck with iTunes.

Without being able to change music on it I was pretty much out of luck.

I got the feeling that Apple had done this on purpose to make me buy a new one (this one was about 8 years old) so it really bugged me.

So anyway, I was thinking I maybe could access it from Linux instead. I found the GTKPod-package. After hassling a bit with booting my Mac from a Linux USB stick I was good to go.

I accidentally installed Ubuntu 16 and apparently it was missing some of the repositories for gtkpod. I tried to compile it but it turned out to be easier just to add the missing repository (the link below should contain the link to the repository)

But I was still out of luck. It turned out to be the libgpod version - the newer versions does not seem to support the iPod Shuffle 2nd generation properly. I found the answer in this thread: http://ubuntuforums.org/showthread.php?t=1333161

In particular it is Br0ziliy reply that gave me the answer: First install gtkpod:

sudo apt-get install gtkpod

Then install the old version of libgpod:

sudo apt-get install intltool libglib2.0-dev libplist-dev wget "http://sourceforge.net/projects/gtkpod/files/libgpod/\ libgpod-0.7.9x/libgpod-0.7.90.tar.gz/download" mv download libgpod-0.7.90.tar.gz tar zxvf libgpod-0.7.90.tar.gz cd libgpod-0.7.90/ ./configure --prefix=/opt/ make sudo make install

And then create a start script:

cat > /tmp/gtkpod<<EOF #!/bin/bash LD_PRELOAD=/opt/lib/libgpod.so.4.2.0 /usr/bin/gtkpod.bin EOF chmod 755 /tmp/gtkpod sudo mv /usr/bin/gtkpod /usr/bin/gtkpod.bin sudo mv /tmp/gtkpod /usr/bin/gtkpod

[fingertwister]

Note to self - remember to set kSecAttrAccount and kSecAttrService when working with the keychain.

[fingertwister]

I was building a paged scrollview where I needed to temporarily suspend the scroll in one direction. More specifically, I was building some signup forms and I wanted to disable swipe to the next page until the user has entered all data for the current page.

For various reasons I needed to populate the entire scroll view with all pages in advance so just adding stuff to it as the user wen along was not really an option.

Here is the code snippet I came up with.

The basic idea is to check if we are at the last available page, check the direction the user scrolled in. If the user tried to scroll past the last avaialble page, reset the scroll view content offset to the offset of the current page.

The scrollEnabled stunt is needed to avoid the page scroll deceleration offsetting the scroll view (try to remove it and you will see what I mean).

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {

// disable scroll to next page if needed if (self.numAvailablePages <= (self.pageControl.currentPage + 1)) { if (self.scrollView.contentOffset.x >= self.currentScrollOffset.x) { self.scrollView.contentOffset = self.currentScrollOffset; UIScrollView* sv = self.scrollView; sv.scrollEnabled = NO; [[NSOperationQueue mainQueue] addOperationWithBlock:^{ sv.scrollEnabled = YES; }]; } } }

[fingertwister]

Let’s Encrypt is a free, automated, and open certificate authority brought to you by the Internet Security Research Group (ISRG). ISRG is a California public benefit corporation, and is recognized by the IRS as a tax-exempt organization under Section 501(c)(3) of the Internal Revenue Code.

In short: Game changer in the ssl world. May actually make ssl available for everyone.

[fingertwister]

Nomad is a collection of world-class command line utilities for iOS development.

I cannot believe I missed this.

[fingertwister]

Cocoapods assertion failure

In XCode 7.0 I needed to update my pods. I ran:

pod update

But got the following error

ruby[13920:2020230] [MT] DVTAssertions: ASSERTION FAILURE in /Library/Caches/com.apple.xbs/Sources/IDEFrameworks/IDEFrameworks-8227/IDEFoundation/Initialization/IDEInitialization.m:590 Details: Assertion failed: _initializationCompletedSuccessfully Function: BOOL IDEIsInitializedForUserInteraction() Thread: <nsthread:>{number = 1, name = main} Hints: None Backtrace: 0 0x000000010917aa5c -[DVTAssertionHandler handleFailureInFunction:fileName:lineNumber:assertionSignature:messageFormat:arguments:] (in DVTFoundation) 1 0x000000010917a1e9 _DVTAssertionHandler (in DVTFoundation) 2 0x000000010917a455 _DVTAssertionFailureHandler (in DVTFoundation) 3 0x000000010917a3b7 _DVTAssertionFailureHandler (in DVTFoundation) 4 0x000000010ae42f5c IDEIsInitializedForUserInteraction (in IDEFoundation) 5 0x000000010da59eb9 +[PBXProject projectWithFile:errorHandler:readOnly:] (in DevToolsCore) 6 0x000000010da5ba3e +[PBXProject projectWithFile:errorHandler:] (in DevToolsCore) 7 0x00007fff8eb3bf44 ffi_call_unix64 (in libffi.dylib)

I tried gem install xcodeproj, xcode-select -r and a few other things but nothing solved it.

It turned out I needed to re-install cocoapods from scratch:

sudo gem uninstall cocoapods

sudo gem install cocoapods

pod install

[fingertwister]

ffmpeg downscaling command

The ffmpeg scale filter parameters are not very well documented. Especially not how to add them as filter_complex params, there are not many examples and so on.

Downscaling is an interesting topic and the difference is HUGE if you compare downscaling out of the box with downscaling using tweaked parameters.

This snippet scales input.mov to 960x540 using a lanczos algorithm doing full chroma interpolation and so on.

ffmpeg -i input.mov \ -filter_complex 'scale=w=960:h=540:'\ 'flags=lanczos+full_chroma_int+full_chroma_inp+accurate_rnd:'\ 'src_range=0:dst_range=1' \ -c:v libx264 \ -preset slow \ -crf 20 \ output.mp4

(To be honest I am not entirely sure on what the src_range and dst_range parameters do but configuring them this way seemed to give a better result, deeper colors or punchier contrast or something like that)

UPDATE: Add this flag to add compatibility with QuickTime player

-pix_fmt yuv420p

[eugenehp]

iojs/io.js

[fingertwister]

io.js - Evented IO for V8 JavaScript

[eugenehp]

[fingertwister]

A presentation on how to render water using webgl

[eugenehp]

[fingertwister]

JSON Web Token (JWT) is a compact URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is digitally signed using JSON Web Signature (JWS).

[eugenehp]

Some of the processing.js examples

[fingertwister]

[fingertwister]

Note to self :)