Sam Stewart

When to call, how to use our friend: [super dealloc]

Sat, 09 Jun 2012 08:32:07 -0700

I’ve been refactoring an application for a client and continually ran into a peculiar error involving malloc. Apparently the code was trying to access an object which had already been released. I pored over each dealloc method until I narrowed the issue down by painful trial and error. The release statements appeared normal but I began to notice the [super dealloc] call was at the top of every dealloc method before the code released the other instance variables. Usually I place my [super dealloc] methods at the end of each dealloc, by convention, but I’ve never thought there was a good reason for doing so.

Until today. The crash which took me days to track down immediately disappeared when I moved the [super dealloc] call to the top of the dealloc method. The issue was sporadic and did not occur in every dealloc method which made it especially confusing. When you call [super dealloc] you are effectively destroying the heap space allocated for yourself thus invalidating all pointer references. If you then try to release the other instance variables, the system throws a cryptic error. This link on StackOverflow sums up the problem: http://stackoverflow.com/a/4566488

Inventing on Principal Some excellent career advice in addition...

Sat, 26 May 2012 20:04:07 -0700

Inventing on Principal

Some excellent career advice in addition to amazing UI demos

Don't touch the UI in init methods

Sat, 26 May 2012 10:44:47 -0700

When overriding or adding an init method to a UIView or UIViewController do not touch any elements of the view hiearchay as this behavior can lead to unintended side effects. A common error is to do the following in an init method:

self.view.autoresizingMask = …;

This seemingly innocuous line of code will actually start the view loading and call loadView, viewDidLoad, etc. since self.view is really a getter. Of course, it is bad practice to load the entire view hierarchy from the init method; that should be done by the parent view when it’s ready to ensure “lazy loading”. The easy solution is to abstain from touching any UIView elements in the initializers; wait until viewDidLoad.

Using #pragma in Obejctive-C

Sat, 19 May 2012 17:15:29 -0700

When dealing with large files developers can add “#pragma mark …” statements to clarify different sections. This is especially helpful when viewing the method listing in XCode.

To further demarcate the separations, “#pragma mark -” creates a horizontal line in the method listing. Up to this point I have thus been writing:

#pragma mark -
#pragma mark Calculation methods

Today I learned you can combine these two lines into:

#pragma mark - Calculation Methods

A small change, but it will eliminate one more unnecessary line of code!

Loving Ruby..

Wed, 16 May 2012 18:38:59 -0700

Loving Ruby..:

Quickly check for instance variables which have been already set!

Xcode 4.3.2 Excessive CPU Usage Fix

Wed, 16 May 2012 12:13:03 -0700

Xcode 4.3.2 Excessive CPU Usage Fix:

Apparently the new Xcode installer does not properly switch out thexcodebuildtool.

Python 'is' vs '==' operator

Mon, 14 May 2012 11:15:41 -0700

Python 'is' vs '==' operator

Run a specific Nose test

Sun, 08 Apr 2012 07:41:44 -0700

Run a specific Nose test

Display Logging Output when Running Nose Unit Tests

Sun, 08 Apr 2012 07:35:41 -0700

Display Logging Output when Running Nose Unit Tests:

By default, nose consumes the output generated by the logging module but you can easily disable this behavior with the —nologcapture flag.

Previous Command (Up-Arrow) in Emacs Shell

Mon, 02 Apr 2012 07:19:21 -0700

Previous Command (Up-Arrow) in Emacs Shell:

Useful keyboard shortcut (instead of up arrow) for using previous command in Emacs shell.

Use Option as Emacs Meta key on Mac OS X

Fri, 30 Mar 2012 15:53:18 -0700

Use Option as Emacs Meta key on Mac OS X:

Useful tip for using Option/Alt key in Terminal as Emacs meta key.

"When calculators can do multidigit long division in a microsecond, graph complicated functions at..."

Fri, 30 Mar 2012 13:23:16 -0700

“When calculators can do multidigit long division in a microsecond, graph complicated functions at the push of a button, and instantaneously calculate derivatives and [[integrals, serious questions arise about what is important in the mathematics curriculum and what it means to learn mathematics. More than ever, mathematics must include the mastery of concepts instead of mere memorization and the following of procedures. More than ever, school mathematics must include an understanding of how to use technology to arrive meaningfully at solutions to problems instead of endless attention to increasingly outdated computational tedium.”

- National Council of Teachers of Mathematics, Commonsense Facts to Clear the Air

Error: "gcc: error trying to exec 'cc1plus': execvp: No such file or directory"

Wed, 28 Mar 2012 19:32:51 -0700

Error: "gcc: error trying to exec 'cc1plus': execvp: No such file or directory"

Unix dig command

Wed, 28 Mar 2012 19:01:42 -0700

Unix dig command:

Query DNS servers about an IP address or URL

Unix & Linux Background Job Management

Wed, 28 Mar 2012 19:00:33 -0700

Unix & Linux Background Job Management

Insert Multiple Entries with MySQL

Fri, 16 Mar 2012 20:39:56 -0700

Insert Multiple Entries with MySQL

Python Raw Strings

Sat, 10 Mar 2012 09:54:03 -0800

Quite interesting, didn’t know this:

When an “r” or “R” prefix is present, a character following a backslash is included in the string without change, and all backslashes are left in the string. For example, the string literal r"\n" consists of two characters: a backslash and a lowercase “n”. String quotes can be escaped with a backslash, but the backslash remains in the string; for example, r"\"" is a valid string literal consisting of two characters: a backslash and a double quote; r"\" is not a valid string literal (even a raw string cannot end in an odd number of backslashes). Specifically, a raw string cannot end in a single backslash (since the backslash would escape the following quote character). Note also that a single backslash followed by a newline is interpreted as those two characters as part of the string, not as a line continuation.

Exclude Java Files in Eclipse

Mon, 05 Mar 2012 16:03:57 -0800

Exclude Java Files in Eclipse:

Especially helpful when using external libraries!

"It is not knowledge, but the act of learning, not possession but the act of getting there, which..."

Mon, 05 Mar 2012 15:13:04 -0800

“It is not knowledge, but the act of learning, not possession but the act of getting there, which grants the greatest enjoyment. When I have clarified and exhausted a subject, then I turn away from it, in order to go into darkness again. The never-satisfied man is so strange; if he has completed a structure, then it is not in order to dwell in it peacefully, but in order to begin another. I imagine the world conqueror must feel thus, who, after one kingdom is scarcely conquered, stretches out his arms for others.”

- Carl Friedrich Gauss

Location of Python Standard Libraries

Sun, 04 Mar 2012 15:53:01 -0800

Location of Python Standard Libraries:

Simply use the os.prefix property.