Archive for category iOS Development

Finding Xcode’s Predefined Macros for iOS Devices (updated)

Update to my old post:…or-ios-devices

To find the iOS predefined macros For Xcode 6, type this into the terminal:

llvm-gcc -arch armv7 -dM -E – < /dev/null | sort

(Yes, there is a single dash by itself.)
Change the -arch option to “armv6” or “armv7” or “armv7s” as needed.


Solid Coding: Autoresize Masks

UITableView cell contains UILabel set with mask to pin the left and right and allow change to width

If the frame of the cell shrinks past the origin of the UILabel, then the right side of the label will be beyond the right side of the cell frame when it was previously contained entirely inside the frame.

This can be detected with Assertions in the ‘setFrame’ method or you can override the incoming frame to prevent the cell’s frame from shrinking so small that the expansion will be incorrect.

NSTimer Out of Sync with Device Clock?

I encountered this puzzle recently:  How does a 60-second, repeating, NSTimer drift way out of sync with the iPhone’s system clock?  The timer was created with a fireDate that was on the even minute with the clock.  It fires at 11:02:00 AM and 11:03:00 AM, etc.  But users report the timer firing at 1:23:30 PM for example.

(And we are not talking about timers not firing because the run loop mode changed temporarily.)

It turns out that the clue is the word “iPhone”. The NSTimer does not drift from the system clock, the system clock drifts from the NSTimer.  The iPhone can have its clock adjusted during the day by the cellular service, especially if the phone goes out of service and comes back. (Changing locations to a different time zone probably triggers it too.)

You can make it happen by just setting the device clock manually.  When you pic a new time, it jumps to the hour and minute chosen, but with zero seconds.  The iOS honors the repeat rate from the last firing and adjusts the fireDate accordingly.

So if you need to stay tuned to the clock, you’ll need to update the fireDate on the NSTimer when you receive the significant time update notification.


Xcode 4.3.2 pains and tips 1

So far, XCode 4.3.2 has been irritating.  It crashes far too often.  But here is some of what I’ve learned:

Get a funny response from copy and paste in Xcode? Strange response from Xcode from undo?  Did the change not appear in Xcode?  Did lines disappear from Xcode?

These kinds of things usually indicate that a crash will be happening soon.

Sometimes I can recover by changing to another file, then changing back. This does seem to help keep Xcode running.

My editing habits probably contributed a little. I tend to scroll around, then use undo-redo in quick succession as a way to go back to where I was in the file.  Usually this was fine in previous versions, but Xcode 4.3.2 seems to crash a lot right after I do this.



Finding Xcode’s Pre-defined Macros for iOS Devices

I regret not making better notes about exactly why I was looking for a full list of the pre-defined macros Apple made available for iOS development.  I usually like starting an entry talking about why I was trying to solve a particular problem.  While I made a note to write up what I found, I did not note why I needed it at the time.  Assuming you are reading this because you need or might need such a thing, I’ll write on.

Some of the pre-defined macros are published in Apple’s documentation, but not all.  (Well, as far as I remember anyway.)  I feel the most confident that I didn’t miss one that could solve a problem when I get the list from the compiler itself.

While searching the internet I found instructions to use

I changed ‘i386’ to ‘armv6’ and ‘armv7’ but that failed on my setup.  I don’t really know if I messed something up in the /Developer folder or if this line just generally won’t work for ARM.

The error message mentioned a missing file and after finding it, I changed the above command to this:

For Xcode 3.2.5:

For Xcode 4.2.1

Change the “armv6” to “armv7” and vice-versa as needed.

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Fix to Symbolicate System Symbols in iOS 5.0.1 (9A405) Crash Logs

I found this one many weeks back and had it in my to-do list for the blog.  Now that 5.1 is out, I feel guilty I didn’t write it up sooner.  But then, my day job is keeping me very busy.

I had a long period where I could not fully symbolicate crash logs that were made by iOS 5.0.1 devices.  The symbols of my app would be symbolicated, but the system symbols of the device would not.  I was especially frustrated because a coworker with the exact same version of XCode could symbolicate those system symbols with no problem.  Neither of us knew why.

After a huge amount of searching with Google and reading items on,  I finally found a note saying the symbols in the iPhone 4S were corrupted somehow and they should be replaced with symbols from another device.  I don’t know if there was a problem with all the iPhone 4S devices, or just some of them or just early ones.

As much as I tried to do this,  I still could not symbolicate properly.  I triple-searched my computer for all copies of symbols for 5.0.1 (9A405) and removed them.  (You can compress them into .zip files if you want to keep them just in case.)

What I needed to know was to look in ~/Library/Developer/Xcode/iOS DeviceSupport   Xcode 4.2 had been putting device symbol information in there.  Once I got rid of that folder, and attached a device, XCode pulled a new copy of the symbols and symbolication worked like a charm.

Top top it all off,  something about the symbolication script in XCode 4.2 works better than any of the previous symbolication scripts, either from Apple or from any developer site.  While symbolication inside XCode can be horribly slow, it does work pretty well.

Hope that helps

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XCode 4 – Stopping in the Debugger on NSAssert

I’m not sure if XCode 4 makes this technique unnecessary. Since I originally wrote this, I’ve seen XCode 4.0.2 stop at NSAssert on its own, without me setting this breakpoint. But it may be helpful to someone somehow. So here it is:

Xcode 3: Run Menu -> “Manage Breakpoints”
XCode 4: Go to the breakpoint navigator.

Click the + button at the bottom of the navigator, select “Add Symbolic Breakpoint…” from the contextual menu that appears.

In the “Symbol” box, enter

Then click “Done”. (NOTE: this is the default assertion handler. If you are using a custom assertion handler, you probably need to specify a symbol for its object and method.)

Now execution will break immediately on assertion failure. And very usefully, XCode shows the nearest source code of the stack, not the assembly of the assertion handler.

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XCode 4: Conversion Problem

Did you try to build your project in XCode 4 for the first time and get an error that starts with “There is no SDK with the name or path”?

That happened to me recently.  And the path given in the message had nothing to do with SDK’s.  In fact it was an open-source sub-project I was using.

I Googled for the answer, but mostly just found references to posts on how to fix actual SDK path problems.

It turned out that the problem was how XCode 4 looked at the sub-project.  Somehow, XCode 4 had noticed a missing Base SDK, had a static library as the product, and assumed it was a Mac OS X project.

I closed the project and opened the sub-project directly.  I corrected the project settings back to iOS and it built correctly. Closing and going back to the first project, the build now built correctly (with some warnings that I did not recall from XCode 3.)



XCode 4 Column-Wise Copy-Paste Changed

One of the strangely useful features of XCode 3 and 4 is the column-wise copy-and-paste.  But a change in XCode 4 takes away column-pasting.

Not seen this before?  Just hold the option-key while you drag a selection in XCode 3 or 4.  The text cursor will be replaced with a “+” and you can select columns of text right out of the middle of a document. (It helps if the text has vertically-oriented columns.)  It made me chuckle the first time I used it to select a column of tabs and paste them into the middle of a bunch of declarations to move them over all at once.

Pasting in a column required adjustment in XCode 3.  It would paste in the same vertical fashion as the copy, so it was easy to write over quite a bit if you weren’t careful with giving yourself space.  But then that made it interesting too.  I copied a column of member variables and pasted them all at the ends of a series of @property directives in one shot.  The same for the series of @synthesize directives.

In XCode 4, while you can copy a column, pasting it is essentially the same as having copied from any other text. Pasting does not happen in columns.

Admittedly, I did convert my columns to regular text pasting with a quick paste and re-copy in an empty file once in a while because that is what was needed.

Still,  I think I’ll miss the ability to paste in a column.

Modal View appearing the wrong location?

Is calling presentModalViewController: while a keyboard is visible making your view appear in the wrong place on-screen?

Try sending the message to a different part of the view-controller hierarchy.

I had this problem recently and was getting ready to start hunting down the current first-responder when I lucked into a quicker answer:  change the receiver from the current view controller to the navigation controller. The navigation controller handles getting objects to resign first-repsonder status without any more code from me.

Getting the view dismissed when done is easy too.  Just send the dismiss message to the modal view’s navigationController.