mikeash.com: NSBlog

Tags: fridayqna defensive objectivec cocoaWelcome back to another word-laden edition of Friday Q&A. About a year ago, I wrote a post on defensive programming. That post covered defensive programming in a general sense, and Scott Gould has requested that I write one specific to various standard Cocoa practices, which is what I will be talking about today.

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Friday Q&A 2010-08-12: Implementing NSCoding at 2010-08-13 16:35

Tags: fridayqna cocoa objectivec nscoding serializationWelcome back to another frightening edition of Friday Q&A. This time around, friend and local OS X coder Jose Vazquez has suggested that I discuss how to implement NSCoding in Objective-C classes.

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Friday Q&A 2010-07-30: Zeroing Weak References to CoreFoundation Objects at 2010-07-30 19:01

Tags: fridayqna corefoundation hack evilIt's time for another friendly edition of Friday Q&A. For my last Friday Q&A, I talked about MAZeroingWeakRef and how it's implemented for pure Objective-C objects. For this one, I'm going to discuss the crazy hacks I implemented to make it work with toll-free bridged CoreFoundation objects as well.

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Friday Q&A 2010-07-16: Zeroing Weak References in Objective-C at 2010-07-16 20:18

Tags: fridayqna objectivec garbagecollection hackIt's that time of the biweek again. For this week's Friday Q&A, Mike Shields has suggested that I talk about weak references in Objective-C, and specifically zeroing weak references. I've gone a bit further and actually implemented a class that provides zeroing weak references in Objective-C using manual memory management.

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Friday Q&A 2010-07-02: Background Timers at 2010-07-02 16:45

Tags: fridayqna blocks gcdWelcome back to another Friday Q&A. This week I'm departing from my usual user-driven format to present a class I've written for what I'm calling "background timers", and discuss potential uses for it.

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Friday Q&A 2010-06-18: Implementing Equality and Hashing at 2010-06-18 14:48

Tags: fridayqna isequal hash cocoa objectivecWelcome back to a late edition of Friday Q&A. WWDC pushed the schedule back one week, but it's finally time for another one. This week, I'm going to discuss the implementation of equality and hashing in Cocoa, a topic suggested by Steven Degutis.

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Friday Q&A 2010-05-28: Leopard Collection Classes at 2010-05-28 16:43

Tags: fridayqna collections cocoaWelcome back to another edition of Friday Q&A. For this week's post, I'm going to talk about three somewhat obscure collections classes that were introduced to Cocoa in 10.5: NSPointerArray, NSHashTable, and NSMapTable, a topic suggested by Phil Holland.

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Friday Q&A 2010-05-14: What Every Apple Programmer Should Know at 2010-05-14 15:36

Tags: fridayqna apple cocoa adviceWelcome back to another Friday Q&A. This week, Quentin Carnicelli (who is heavily involved in generating my paychecks) has suggested that I talk about things that every Apple programmer should know. In other words, common Cocoa design and implementation decisions that I'd prefer Apple not to make.

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Friday Q&A 2010-04-30: Dealing with Retain Cycles at 2010-04-30 15:29

Tags: fridayqna cocoa memory retain releaseHappy iPad 3G day to everyone. Whether you're waiting in line, waiting for the delivery guy, or just pining at home like I am, you can fill your idle moments with another edition of Friday Q&A. This week, Filip van der Meeren has suggested that I discuss retain cycles and how to deal with them.

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Friday Q&A 2010-04-23: Implementing a Custom Slider at 2010-04-23 16:01

Tags: fridayqna cocoa controlsWelcome to another chilling edition of Friday Q&A. While I hope to be soaring over the scenic Shenandoah Valley on this fine Friday, I have taken the precaution of preparing my post in advance, so that you may see it even while I am incommunicado. Such is the magic of the modern world. This week, Michael Crawford has suggested that I give in example of implementing a custom control in Cocoa.

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Friday Q&A 2010-04-16: Implementing Fast Enumeration at 2010-04-16 16:35

Tags: fridayqna objectivec enumerationLast week I discussed the various options available in Objective-C for enumerating over a collection This week I'm going to finish up the discussion of enumeration with a guide on how to implement Fast Enumeration in your own program.

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Friday Q&A 2010-04-09: Comparison of Objective-C Enumeration Techniques at 2010-04-09 11:17

Tags: fridayqna nsfastenumeration objectivecWelcome back to another edition of Friday Q&A. Preston Sumner has suggested that I talk about different ways of enumerating over collections in Cocoa, and how to implement Fast Enumeration. This will be a two part series: this week I will look at the different enumeration techniques and their pros and cons, and then next week I will take you through implementing Fast Enumeration on a custom object.

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Friday Q&A 2010-04-02: OpenCL Basics at 2010-04-02 11:28

Tags: fridayqna openclI'm back in action at last, so it's time for another Friday Q&A. This week, both someone named "charles" and Brian Olsen have suggested that I talk about OpenCL, so I'm going to go through the basics of what OpenCL is and how to do some simple computation with it.

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Friday Q&A 2010-03-05: Compound Futures at 2010-03-05 13:53

Tags: fridayqna futures blocksWelcome back to another thrilling edition of Friday Q&A. This week I want to extend my discussion from last week about futures, and talk about compound futures, an extension to the basic futures system that I developed previously.

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Friday Q&A 2010-02-26: Futures at 2010-02-26 18:19

Tags: fridayqna futures blocksWelcome back to another shiny edition of Friday Q&A. Guy English suggested taking a look at implementing futures in Objective-C using blocks, and for this week's post I'm going to talk about the futures implementation that I built.

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Friday Q&A 2010-02-19: Character Encodings at 2010-02-19 22:15

Tags: fridayqna unicode encoding textIt's another Friday and another Friday Q&A. For this week's post, Joshua Pokotilow has suggested that I talk about character encodings, so I want to give a basic tour of just what a character encoding is, how it works, and useful details about common encodings.

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Friday Q&A 2010-02-12: Trampolining Blocks with Mutable Code at 2010-02-12 18:20

Tags: fridayqna blocks trampoline assembly evilWelcome to another edition of Friday Q&A, where deep technical talk and complete insanity combine! This week, I'm going to take a quick break from my usual reader-driven format and talk about a little toy I built earlier in the week, an adapter between blocks and more traditional function-pointer-based callback systems.

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Friday Q&A 2010-02-05: Error Returns with Continuation Passing Style at 2010-02-05 18:36

Tags: fridayqna blocks objectivec continuations errorhandlingThe Earth has moved 6.9 degrees around the Sun since my last post, which means it's time for another edition of Friday Q&A. This 6.9-degree segment, Guy English has suggested that I talk about the use of continuation passing style to simplify error returns in Objective-C code.

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Friday Q&A 2010-01-29: Method Replacement for Fun and Profit at 2010-01-29 19:00

Tags: fridayqna objectivec swizzling override evilIt's that time of the week again. For this week's Friday Q&A Mike Shields has suggested that I talk about method replacement and method swizzling in Objective-C.

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Friday Q&A 2010-01-22: Toll Free Bridging Internals at 2010-01-22 16:57

Tags: fridayqna corefoundation bridgingIt's been a week, and once again, it's time for a Friday Q&A. For this week's edition, I'm going to talk about how toll-free bridging works, a topic suggested by Jonathan Mitchell.

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Friday Q&A 2010-01-15: Stack and Heap Objects in Objective-C at 2010-01-15 21:58

Tags: fridayqna stack heap memoryWelcome to another Friday Q&A. I survived my travel and am (just barely) ready to write another exciting edition. This week's topic comes from Gwynne, who asked why Objective-C only uses heap objects, and no stack objects.

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Friday Q&A 2010-01-08: NSNotificationQueue at 2010-01-08 07:21

Tags: fridayqna cocoa notificationsIt's that time of the week again. No, it's not just time to go get drunk, but time for Friday Q&A! This week's topic, suggested by Christopher Lloyd of Cocotron (a really neat open source project that lets you write Objective-C/Cocoa code for non-Mac platforms like Windows), is NSNotificationQueue, a little-known, poorly-understood, but handy Foundation class.

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Friday Q&A 2010-01-01: NSRunLoop Internals at 2010-01-01 10:43

Tags: fridayqna cocoa runloopIt's the first Friday of the new year, and that means it's time for the first Friday Q&A of 2010. This week, I'm taking Dave DeLong's suggestion of talking about NSRunLoop internals.

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Friday Q&A 2009-12-18: Highlights From a Year of Friday Q&A at 2009-12-18 11:18

Tags: fridayqna pointlessIt's hard to believe that it's been a full year (minus a day) since my first Friday Q&A. It's become more successful than I thought possible, and many kind and obviously deluded people have said great things about it to me. Since I'm feeling lazy this week, I thought I'd pull up some highlights from the past year rather than write anything new.

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Friday Q&A 2009-12-11: A GCD Case Study: Building an HTTP Server at 2009-12-11 23:58

Tags: fridayqna gcd http networking generatorsIt's time for another wintry edition of Friday Q&A. From the comfort of your toasty-warm homes, you can read about building an HTTP server using Grand Central Dispatch, a topic suggested by Steven Degutis.

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Friday Q&A 2009-10-30: Generators in Objective-C at 2009-10-30 16:59

Tags: fridayqna generatorsIt's Friday again and time for another Friday Q&A. This week I'm going to discuss a framework for creating generators in Objective-C. I'm indulging myself a bit with this, because nobody suggested it, but nothing in my suggestion bank inspired me this time around, so I decided to go with something of my own.

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Friday Q&A 2009-10-23: A Preview of Coming Attractions at 2009-10-23 15:45

Tags: fridayqna generatorsI'm afraid that I ran out of time this week and wasn't able to put together a real Friday Q&A. However, as a preview of what I'll be talking about next week, check out the MAGenerator project in my public subversion repository.

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Friday Q&A 2009-10-16: Creating a Blocks-Based Object System at 2009-10-16 15:50

Tags: fridayqna blocks evilIt's Friday again, and that means another Friday Q&A. This week, Guy English proposed talking about a blocks-based object system, and that is what I will do. The system I've developed is a rudimentary system for doing object-oriented programming in pure C (plus blocks), and I'll discuss how it works and how to use it.

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Friday Q&A 2009-10-09: Defensive Programming at 2009-10-09 16:03

Tags: fridayqna defensiveIt's that time of the week again. This week I'm going to discuss defensive programming, a topic suggested by Ed Wynne.

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Friday Q&A 2009-10-02: Care and Feeding of Singletons at 2009-10-02 15:59

Tags: fridayqna cocoa objective-c singletonIt's time for another Friday Q&A. I hope everyone who had a chance to go to C4 had a good time and is back home safe and sound. This week I'm going to discuss singletons, both how to make them and when to use them, as suggested by Jon Trainer.

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Friday Q&A 2009-09-25: GCD Practicum at 2009-09-25 11:52

Tags: fridayqna gcd performance sourcecodeWelcome back to another Friday Q&A. I'm off to C4 today (hope to see you there!) but I've prepared this in advance so everyone stuck at home (or worse, work) can at least have something interesting to read. Over the past four weeks I've introduced Grand Central Dispatch and discussed the various facilities it provides. In Part I I talked about the basics of GCD and how to use dispatch queues. In Part II I discussed how to use GCD to extract more performance from multi-core machines. In Part III I discussed GCD's event dispatching mechanism, and in Part IV I took care of various odds and ends that I hadn't covered before. This week I'm going to examine a practical application of using GCD to speed up the production of thumbnails for a large quantity of images, a topic suggested by Willie Abrams.

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Friday Q&A 2009-09-18: Intro to Grand Central Dispatch, Part IV: Odds and Ends at 2009-09-18 17:23

Tags: fridayqna gcd performanceIt's that time of the week again. Over the past three weeks I've introduced you to the major pieces Grand Central Dispatch, an exciting new API for parallel processing and event handling in Snow Leopard. The first week I covered basic concepts and dispatch queues. The second week I discussed how to use dispatch queues for parallel processing on multi-core computers. The third week I covered GCD's event handling system. This week I'm going to cover various odds and ends which I didn't get to before: dispatch queue suspension and targeting, semaphores, and one-time initialization.

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Friday Q&A 2009-09-11: Intro to Grand Central Dispatch, Part III: Dispatch Sources at 2009-09-11 15:28

Tags: fridayqna gcd performanceWelcome back to another Friday Q&A. This week I continue the discussion of Grand Central Dispatch from the past two weeks. In the last two weeks I mainly focused on dispatch queues. This week I'm going to examine dispatch sources, how they work, and how to use them.

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Friday Q&A 2009-09-04: Intro to Grand Central Dispatch, Part II: Multi-Core Performance at 2009-09-04 01:51

Tags: fridayqna gcd performanceWelcome back to Friday Q&A. Last week I discussed the basics of Grand Central Dispatch, an exciting new technology in Snow Leopard. This week I'm going to dive deeper into GCD and look at how you can use GCD to take advantage of multi-core processors to speed up computation. This post assumes that you've read last week's edition, so be sure to do that if you haven't already.

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Friday Q&A 2009-08-28: Intro to Grand Central Dispatch, Part I: Basics and Dispatch Queues at 2009-08-28 14:16

Tags: fridayqna gcd performanceWelcome back to Friday Q&A. This week's edition lines up with Apple's release of Snow Leopard, so I'm going to take this opportunity to open up the discussion on previously NDA'd technologies and talk about some of the cool stuff now available in Snow Leopard. For this week I'm going to start what I plan to be an ongoing series on Grand Central Dispatch, a topic suggested by Chris Liscio.

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Friday Q&A 2009-08-21: Writing Vararg Macros and Functions at 2009-08-21 15:15

Tags: fridayqna c vararg macroWelcome to another Friday Q&A, where all references are strong and all values are above average. This week I'm going to talk about how to write macros and functions that take variable arguments in C, as suggested by Damien Sorresso.

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Friday Q&A 2009-08-14: Practical Blocks at 2009-08-14 20:06

Tags: fridayqna blocksWelcome back to another edition of Friday Q&A. I'm back from my break and ready to bring you more programming goodies. This week I want to take Landon Fuller's suggestion to write a followup to my original Friday Q&A on blocks now that the design is finalized and code available for them.

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Friday Q&A 2009-07-17: Format Strings Tips and Tricks at 2009-07-17 15:21

Tags: fridayqna cGreetings and welcome back to Friday Q&A. This week I'm going to discuss some tips and tricks for using printf-style format strings in C, as suggested by Kevin Avila.

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Friday Q&A 2009-07-10: Type Specifiers in C, Part 3 at 2009-07-10 13:00

Tags: fridayqna cHere at last is the conclusion to Friday Q&A's three-part series on C type specifiers. The first week I discussed const and restrict. Last week I discussed the basics of volatile and why it's not very useful. This week I'm going to finish up by discussing the use of volatile in a multithreaded context.

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Friday Q&A 2009-07-03: Type Specifiers in C, Part 2 at 2009-07-03 13:20

Tags: fridayqna cWelcome to another edition of Friday Q&A. Last week I began to talk about type qualifiers in C, and discussed the meaning and use of the const and restrict qualifiers. This week I will continue with a discussion of the third qualifier, volatile.

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Friday Q&A 2009-06-26: Type Qualifiers in C, Part 1 at 2009-06-26 16:11

Tags: fridayqna cWelcome back to another warm and fuzzy edition of Friday Q&A. This week I'm going to discuss the use of type qualifiers in C, a subject suggested by Nate Vander Wilt.

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Friday Q&A 2009-06-19: Mac OS X Process Memory Statistics at 2009-06-19 13:48

Tags: fridayqna memory performanceWelcome back to another Friday Q&A. Now that WWDC is behind us, I'm back on track to bring you more juicy highly-technical goodness. Maybe I can even get back to doing one a week.... This week I'm going to take André Pang's suggestion of discussing process memory statistics (the stuff you see in Activity Monitor or top) in Mac OS X.

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Friday Q&A 2009-06-05: Introduction to Valgrind at 2009-06-05 15:55

Tags: fridayqna valgrindWelcome back to another late Friday Q&A. My apologies to all of my readers for missing last week's edition. Some family events beyond the scope of this blog prevented me from writing one. And I should probably point out right now that WWDC is almost certainly going to prevent me from writing one next week. This week, however, I do have a post, and I'm going to be talking about Valgrind as suggested by Landon Fuller.

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Friday Q&A 2009-05-22: Objective-C Class Loading and Initialization at 2009-05-23 00:37

Tags: fridayqna objective-cWelcome back to another cromulent Friday Q&A. After taking a few weeks off I intend to resume the regular schedule. We'll see how far that intention takes me, but I'm hopeful. This week I'm going to take Daniel Jalkut's suggestion to discuss class loading and initialization in Objective-C.

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Friday Q&A 2009-04-24: Code Generation with LLVM, Part 2: Fast Objective-C Forwarding at 2009-04-24 01:35

Tags: fridayqna llvmIt's Friday again, and that means another Friday Q&A. As promised, this week's edition will pick up where last week's left off. Last week I discussed the basics of generating code at runtime using LLVM. This week I'm going to build on that base and show how to use LLVM to perform fast forwarding in Objective-C.

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Friday Q&A 2009-04-17: Code Generation with LLVM, Part 1: Basics at 2009-04-17 11:07

Tags: fridayqna llvmWelcome back to another heart-pounding edition of Friday Q&A. Phil Holland and Ed Wynne both suggested that I do something with LLVM, and so I'm going to discuss how to generate and call code at runtime using LLVM. This week I'm going to talk about the basics needed to get up and running with code generation, and then next week in Part 2 I'm going to show how you can use this technique to build a fast Objective-C trampoline object.

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Friday Q&A 2009-04-10: Multithreaded Optimization in ChemicalBurn at 2009-04-10 17:22

Tags: fridayqna chemicalburn performance threadingWelcome to another Friday Q&A, where all the women are strong, all the men are good-looking, and all the programmers are above average. This week, Phil Holland has suggested that I dissect an interesting piece of code from one of my screensavers, so we're going to take a look at ChemicalBurn's multithreaded routing code.

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Friday Q&A 2009-03-27: Objective-C Message Forwarding at 2009-03-27 16:50

Tags: fridayqna objective-cWelcome back to another exciting Friday Q&A. This week I'm going to continue the series on the Objective-C runtime. Yuji Tachikawa suggested talking about how @dynamic properties work in CoreData and I'm going to take that and expand it to talk about message forwarding in general.

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Friday Q&A 2009-03-20: Objective-C Messaging at 2009-03-21 01:59

Tags: fridayqna objective-cWelcome back to another Friday Q&A. This week I'd like to take Joshua Pennington's idea and elaborate on a particular facet last week's topic of the Objective-C runtime, namely messaging. How does messaging work, and what exactly does it do? Read on!

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Friday Q&A 2009-03-13: Intro to the Objective-C Runtime at 2009-03-13 14:13

Tags: fridayqna objective-cWelcome back to another Friday Q&A, on another Friday the 13th. This week I'm going to take Oliver Mooney's suggestion and talk about the Objective-C runtime, how it works, and what it can do for you.

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Friday Q&A 2009-03-06: Using the Clang Static Analyzer at 2009-03-06 22:19

Tags: fridayqna clangWelcome back to another exciting Friday Q&A. This week's topic, suggested by Ed Wynne, will be an overview of the Clang Static Analyzer and an example of how to use it.

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Friday Q&A 2009-02-27: Holistic Optimization at 2009-02-27 04:21

Tags: fridayqna rant performanceWelcome back to Friday Q&A, a bit early this week since I won't be around to post it at the usual time. This week I'm going to cheat a little bit and use a topic that I "suggested" myself. I'll be talking about what I like to call "holistic optimization", which is essentially how to look at optimization within the context of your entire project, rather than bit-swizzling, loop unrolling, and other micro-optimizations.

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Friday Q&A 2009-02-20: The Good and Bad of Distributed Objects at 2009-02-20 20:40

Tags: fridayqna performance cocoa ipcWelcome back to another Friday Q&A. This week I'm going to take Erik's (no last name given) suggestion from my interprocess communication post and expand a bit on Distributed Objects, what makes it so cool, and the problems that it has.

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Friday Q&A 2009-02-13: Operations-Based Parallelization at 2009-02-13 20:31

Tags: fridayqna performance nsoperationqueueWelcome back to Friday Q&A, which this week is also Friday the Thirteenth! Be especially careful, as this is the first of two consecutive Friday the Thirteenths. For this first Friday the Thirteenth I'm going to talk about parallel software design using an "operations" approach (think NSOperation), as suggested by Nikita Zhuk way back when I first started this whole thing.

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Friday Q&A 2009-02-06: Profiling With Shark at 2009-02-06 17:30

Tags: fridayqna shark performanceWelcome back to Friday Q&A.; This week I'm taking Jeff Johnson's idea to discuss optimization and profiling tools.

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Friday Q&A 2009-01-30: Code Injection at 2009-01-30 18:34

Tags: fridayqna codeinjection hack evilWelcome back to another exciting Friday Q&A.; This week I'll be taking Jonathan Mitchell's suggestion to talk about code injection, the various ways to do it, why you'd want to, and why you wouldn't want to.

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Friday Q&A 2009-01-23 at 2009-01-23 21:31

Tags: fridayqna kvoWelcome to the first Friday Q&A; of the new Presidential administration. Unlike Mr. Obama, I'm afraid of change and so this week's edition will be just like all the other ones. This week I'll be taking Jonathan Mitchell's suggestion to talk about how Key-Value Observing (KVO) is actually implemented at the runtime level.

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Friday Q&A 2009-01-16 at 2009-01-16 22:35

Tags: fridayqna ipcHappy Friday to everyone, and welcome back to another Friday Q&A. This week I'll be taking Eren Halici's suggestion to discuss the various ways to do interprocess communication on OS X.

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Friday Q&A 2009-01-09 at 2009-01-09 21:38

Tags: fridayqna threading cocoaGreetings one and all. I caught my mistaken writing of "2008" in this blog post title almost instantly instead of only noticing after I'd already posted it like I did last week, so the year must be coming along. Welcome to the second Friday Q&A of 2009 (and only the fourth in all human history!) where I'll be taking Ed Wynne's suggestion and talking about the various meanings and implications of thread safety as they apply to Mac OS X system frameworks.

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Friday Q&A 2009-01-02 at 2009-01-02 23:06

Tags: fridayqna privateapiIt's a new year, and that means a new Friday Q&A! This week I'm going to take Steven Degutis's suggestion and discuss the ups and downs of using private APIs.

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Friday Q&A 2008-12-26 at 2008-12-26 17:19

Tags: fridayqna blocksWelcome to another Friday Q&A. This week I thought I would take fellow amoeboid Jeff Johnson's suggestion and talk about blocks in Objective-C.

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Friday Q&A 2008-12-19 at 2008-12-20 01:28

Tags: fridayqna threading parallelism performanceGreat response last week. This week I'm going to merge Sam McDonald's question about how I got into doing multithreaded programming and Phil Holland's idea of talking about the different sorts of parallelism available.

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Friday Q&A at 2008-12-13 05:00

Tags: fridayqnaIn an effort to liven up the blog a bit, I thought I would start soliciting topics from the readership. Given the large number of comments on certain past posts and the couple hundred unique hits to my RSS feed URL every day, I'm hoping that this might just work out.

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