6 ms·

Reader-submitted Objective-C / XCode tips of 2012

81 points by cozykozy 14y ago

matttthompson 14y ago
For clarification, this is a list of some reader-submitted tricks and tips from the last month, as a way to bring in the New Year. I'm looking forward to doing more of these in the future, so if anyone has any ideas or suggestions, feel free to tweet them to @NSHipster. Thanks!
- cozykozy 14y ago
  Good point. Updated title accordingly!
- zbowling 14y ago
  Hey Matt, I have some amazing tricks for you but I want to save it for a Cocoaheads talk first. :-) We should get around to doing another. Reimplementing the runtime and foundation and hacking on our Clang fork at Apportable the last 6 months, I've learned some amazingly interesting things.
  - alexkcd 14y ago
    Second that. I was pretty upset that I couldn't make it to the last one. Also, on the tricks front: I was proxying UITableViews to override their layout before UICollectionViews were cool :)
  - orta 14y ago
    zbowling, I would be fascinated to read up on some of the things you've learned. I'm based in NYC / UK so its unlikely I'd end up in the SF based cocoaheads. Any chance of a write-up for us all in the new year?
stephth 14y ago
Displaying his characteristic brilliance and familiarity of Cocoa internals Cédric Luthi submitted a reverse-engineered implementation of the NString equality methods. Fascinating! Forgive my ignorance, but how do you go about and reverse engineer NSString equality? Looking at the code is interesting but what I'd really like to understand is where it comes from and how it was extracted; is it supposed to be close to the original implementation, is it an informed guess based on CFLite, ...? Please be patient and again forgive my ignorance.
- mikeash 14y ago
  I can't say for sure, but I'd assume that he manually decompiled the code in the framework.
- mayoff 14y ago
  He probably used Hopper, which he has tweeted about. http://www.hopperapp.com/ http://www.hopperapp.com/
orta 14y ago
The LLDB View Hierarchy Dump tip is something that I think I can use again and again and again.
- cozykozy 14y ago
  Definitely beats view.backgroundColor = [UIColor redColor];! Though I'm not sure I'll ever to shake that trusty old "debugging" hack.
  - orta 14y ago
    I keep some UIColor categories around so at least I can have prettier colours for debugging. It would be nice to make a variant of the method that (somewhat randomly) colours all views and logs the usual info + the colour out to the console.
  - tszming 14y ago
    Well, I use the same method until I heard the DCIntrospect library (https://github.com/domesticcatsoftware/DCIntrospect https://github.com/domesticcatsoftware/DCIntrospect)
- MaxGabriel 14y ago
  It's super preliminary, but if you're debugging the problem I suspect you're debugging by looking at the view hierarchy (iOS touch handling), this might be helpful: https://github.com/MaxGabriel/debugiOSTouchHandling/blob/master/TouchDebug/UIView%2BTouchDebug.m https://github.com/MaxGabriel/debugiOSTouchHandling/blob/mas...
  - orta 14y ago
    Yeah, I spotted that earlier today actually Max, I think it must have been something related to maintaining cocoapods. The library definitely has potential :)
- jparishy 14y ago
  I mentioned this to Mattt on Twitter but I don't think he saw it. There's a lot you can do at the debugger and recursiveDescription can be called on any UIView or UIView subclass. So if you set a breakpoint you can do something like: (lldb) po [self.view recursiveDescription] from one of your view controllers to dump the hierarchy of that view. This of course will work on any object that is a subclass of UIView, such as a UITableView (subclass of UIScrollView, which is in turn a subclass of UIView), a UITableViewCell (directly inherited from UIView), etc. There's a lot of good information provided by Apple on debugging here: http://developer.apple.com/library/ios/#technotes/tn2239/ http://developer.apple.com/library/ios/#technotes/tn2239/ It's definitely worth the time to go through it all if you spend any time debugging iOS code (and there's a Mac OS X equivalent but I can't speak for its usefulness). I've also started writing a little piece on debugging code with lldb and Xcode, but it's a work in progress: https://gist.github.com/3943317 https://gist.github.com/3943317
orta 14y ago
As these are reader submitted, I thought I would mention that I've just released a library for dealing with multiple analytics providers with a single API: https://github.com/orta/ARAnalytics https://github.com/orta/ARAnalytics
mikeash 14y ago
The suggestion that "+initialize is great for registering NSURLProtocol, NSValueTransformer, and NSIncrementalStore subclasses" is, alas, off the mark. If you use +initialize for anything that needs to be registered before it gets used, you'll end up with a chicken-and-egg problem, because +initialize doesn't run until the class's first use. +initialize is great for one-time setup of class-wide data, but it doesn't work for registering classes with the system when the act of registering is the only thing that causes them to be used.
gdubs 14y ago
One I personally really like is typing "target modules lookup --address" in the debugger, followed by a hex value. Really helpful if your app crashes without an interactive stack trace, as it lets you figure out where the crash occurred in your code.

81 points by cozykozy 14y ago

For clarification, this is a list of some reader-submitted tricks and tips from the last month, as a way to bring in the New Year. I'm looking forward to doing more of these in the future, so if anyone has any ideas or suggestions, feel free to tweet them to @NSHipster. Thanks!

cozykozy 14y ago
Good point. Updated title accordingly!
zbowling 14y ago
Hey Matt, I have some amazing tricks for you but I want to save it for a Cocoaheads talk first. :-) We should get around to doing another. Reimplementing the runtime and foundation and hacking on our Clang fork at Apportable the last 6 months, I've learned some amazingly interesting things.
- alexkcd 14y ago
  Second that. I was pretty upset that I couldn't make it to the last one. Also, on the tricks front: I was proxying UITableViews to override their layout before UICollectionViews were cool :)
- orta 14y ago
  zbowling, I would be fascinated to read up on some of the things you've learned. I'm based in NYC / UK so its unlikely I'd end up in the SF based cocoaheads. Any chance of a write-up for us all in the new year?

stephth 14y ago

Displaying his characteristic brilliance and familiarity of Cocoa internals Cédric Luthi submitted a reverse-engineered implementation of the NString equality methods. Fascinating! Forgive my ignorance, but how do you go about and reverse engineer NSString equality? Looking at the code is interesting but what I'd really like to understand is where it comes from and how it was extracted; is it supposed to be close to the original implementation, is it an informed guess based on CFLite, ...? Please be patient and again forgive my ignorance.

mikeash 14y ago
I can't say for sure, but I'd assume that he manually decompiled the code in the framework.
mayoff 14y ago
He probably used Hopper, which he has tweeted about. http://www.hopperapp.com/ http://www.hopperapp.com/

orta 14y ago

The LLDB View Hierarchy Dump tip is something that I think I can use again and again and again.

cozykozy 14y ago
Definitely beats view.backgroundColor = [UIColor redColor];! Though I'm not sure I'll ever to shake that trusty old "debugging" hack.
- orta 14y ago
  I keep some UIColor categories around so at least I can have prettier colours for debugging. It would be nice to make a variant of the method that (somewhat randomly) colours all views and logs the usual info + the colour out to the console.
- tszming 14y ago
  Well, I use the same method until I heard the DCIntrospect library (https://github.com/domesticcatsoftware/DCIntrospect https://github.com/domesticcatsoftware/DCIntrospect)
MaxGabriel 14y ago
It's super preliminary, but if you're debugging the problem I suspect you're debugging by looking at the view hierarchy (iOS touch handling), this might be helpful: https://github.com/MaxGabriel/debugiOSTouchHandling/blob/master/TouchDebug/UIView%2BTouchDebug.m https://github.com/MaxGabriel/debugiOSTouchHandling/blob/mas...
- orta 14y ago
  Yeah, I spotted that earlier today actually Max, I think it must have been something related to maintaining cocoapods. The library definitely has potential :)
jparishy 14y ago
I mentioned this to Mattt on Twitter but I don't think he saw it. There's a lot you can do at the debugger and recursiveDescription can be called on any UIView or UIView subclass. So if you set a breakpoint you can do something like: (lldb) po [self.view recursiveDescription] from one of your view controllers to dump the hierarchy of that view. This of course will work on any object that is a subclass of UIView, such as a UITableView (subclass of UIScrollView, which is in turn a subclass of UIView), a UITableViewCell (directly inherited from UIView), etc. There's a lot of good information provided by Apple on debugging here: http://developer.apple.com/library/ios/#technotes/tn2239/ http://developer.apple.com/library/ios/#technotes/tn2239/ It's definitely worth the time to go through it all if you spend any time debugging iOS code (and there's a Mac OS X equivalent but I can't speak for its usefulness). I've also started writing a little piece on debugging code with lldb and Xcode, but it's a work in progress: https://gist.github.com/3943317 https://gist.github.com/3943317

orta 14y ago

As these are reader submitted, I thought I would mention that I've just released a library for dealing with multiple analytics providers with a single API: https://github.com/orta/ARAnalytics https://github.com/orta/ARAnalytics

mikeash 14y ago

The suggestion that "+initialize is great for registering NSURLProtocol, NSValueTransformer, and NSIncrementalStore subclasses" is, alas, off the mark. If you use +initialize for anything that needs to be registered before it gets used, you'll end up with a chicken-and-egg problem, because +initialize doesn't run until the class's first use. +initialize is great for one-time setup of class-wide data, but it doesn't work for registering classes with the system when the act of registering is the only thing that causes them to be used.

gdubs 14y ago

One I personally really like is typing "target modules lookup --address" in the debugger, followed by a hex value. Really helpful if your app crashes without an interactive stack trace, as it lets you figure out where the crash occurred in your code.