Our DNA is written in Objective-C

Decompressing Files into Memory

As a hobby project I am working on uncovering hidden treasures that exist on all your iOS devices. Hidden, because there is no Objective-C API for them, Existing, because Apple includes a great deal of open source libraries in iOS, compiled as a dynamic library.

What items exist you can see if you check out what dylibs are there to be seen in “Link Binary with Libraries”. Most entries beginning with lib and ending with dylib can be used. Some people have reported getting rejected for adding the static variants of libraries like libxslt or libarchive, but that’s probably because Apple sees these symbols as duplicate to the ones contained in the dynamic libraries.

We previously looked at libxml2 for parsing HTML (and part 2), today we’ll familiarize ourselves with zlib for decompressing .gz and .zip files.

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Podcast #24 – “Ingest This!”

Some Apple announcements for developers, some insight and some show notes.


Please comment, tweet or mail your suggestions on topics that are of interested to iOS (and by extension Cocoa developers in general).

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Fast Folder Nuking on iOS

I got a strange bug report last week for iCatalog. Deleting of outdated catalogs takes too long, if we couldn’t show a HUD with a spinner while the deletion occurs. That was definitely one of these HUUUUU?! moments. I always thought that file deletion is instant on Unix since only an entry in a file table needs to be removed.

I grabbed an iPad 1 and deleted a 160 MB catalog. Only to find that the whole deletion – a simple NSFileManager removeItemAtPath – took 50 seconds. Uhm, no that is far from ideal to be blocking the main thread and interface for that long.

I played around a bit and over the course of the day, with some great help from several GCD experts on twitter, I pieced together a solution that might interest you if you ever have to delete large amounts of files in an instant. Before Cocoa, on Carbon, OSX offered a method called FSPathMoveObjectToTrashAsync, this is sort of the equivalent for iOS.

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GeoCorder 1.3.2

Here’s another maintenance release fixing a crashing bug in the About section.


  • Fixed: Crash on trying to open usage instructions
  • Added: More detailed explanation of accuracy and filter settings

This update, like the one before it, goes out for the paid version of GeoCorder first. If the issues are resolved once this comes into the store then we’ll update the ad-sponsored version, too.

Update Feb 11th: The update has been approved.

DTRichTextEditor / DTCoreText News

You might have noticed – if you follow the DTCoreText project on GitHub – that I made many changes on this Open Source project. The most recent change was that somebody donated a CocoaPods spec for the project and thus forced me to give it a version number. The reason being that pods are usually pointing to a specific tag in a GitHub repository. This way people using the project via CocoaPods can be certain that they are getting a stable version.

So I stumbled into this, but when trying to think of a good version number I could only come up with “1.0.0”. DTCoreText has matured sufficiently to call it that. Hey, earlier versions made it into quite a few popular apps, including Float. There are tons of performance improvements, additional features and most importantly the parser has been replaced with libxml2. This makes it both faster and able to deal with any kind of HTML you throw at it.

DTCoreText has two parts: first it creates NSAttributedString instances from HTML, second it displays these properly. CATextLayer would be able to take attributed strings, but it ignores paragraph attributes and cannot draw images. DTCoreText  has an ingenious mechanism where you can supply your own UIViews for each attachment.

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Autoingest.java – in Objective-C

We are lobbying since 2009 to get Apple to publish a proper API for downloading all kinds of reports.

The first reaction we got was prohibition of ITC scraping. The second reaction was that Apple created the Mobile ITC app which unfortunately lacks any kind of possibility to get the reports out or get monetary amounts. The third reaction was a half-harted publishing of a Java class that is able to download daily and weekly sales reports.

This changes today, at least if you are like me and feel uneasy to use Java for downloading reports.

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Podcast #023 – “Happy New … February”

We’re rebooting the Cocoanetics Podcast. The last episode had been over a year ago.

Happy New … February


Please comment, tweet or mail your suggestions on topics that are of interested to iOS (and by extension Cocoa developers in general).

The new title song “Cocoa Cookin'” was composed and produced by Jamie Harper.

Radar: “CoreText Line Spacing Bug”

I finally got around to report an annoying bug in CoreText that has been bugging us in DTCoreText until I wrote a method to correct line origins as a workaround. rdar://10810114

The annoying thing about this bug is that it adds visual noise to otherwise pristinely rendered text. Especially on larger font sizes you see that additional space appears before each CTLine that ends with a paragraph break (\n).

UPDATE: This is a duplicate of rdar://9931615.

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Xcode Build Rules

When I moved the default CSS rules into a separate file I was facing the old dilemma: how can I embed this in the static library but still be able to easily add contents to it via Xcode. I previously explained how you can turn any file into a c-Byte-array. But this still required manual work.

I did a bit of researching and found that on regular Linux systems people seem to have a tool named objcopy which can copy files as their are into an object file (.o) which can be linked together to the final binary by the linker. But unfortunately this tool does not come with Xcode. So it is out of the question because I want everybody to be able to build DTCoreText.

Xcode Build Rules come to the rescue. They can automate any kind of preprocessing you like and it turns out they are an easy solution for this very problem.

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iWoman 2.0.5

This is a maintenance update. There was a bug in DTAboutViewController which caused a crash under iOS 5.


  • Fixed: Crash on iOS 5 when opening About Section

The update has been submitted to Apple for approval.

Update Feb 8th: Ready for Sale. It should be available shortly.