Tag Archives: instruments

The development of Contacts2Web

Introduction

contacts2web_512Part of the online course that I took from Stanford on iPhone app development involved choosing a final project. My top-level criteria for choosing a project included:

  • Incorporate several different iOS technologies.
  • Make use of an external web service and API.
  • Interaction with an external web site.

What I eventually settled on was a concept for allowing a user to view and edit their iPhone Address Book contacts both within an app as well as in a full web browser.

This functionality is already available as a service now at iCloud.com. My plan was to start with this capability and over time begin to add new functionality (social sharing, etc).

The Contacts2Web app is now available in the App Store.  In this document, I will cover some of the details that went into developing the app.

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Using code generated flags to debug with Instruments

I discovered a great debugging tool today from the article Flags: very useful when debugging with Instruments   The article talks about how to put up flags from your code that appear in the Instruments window.    This is a feature that is new to Instruments 4.0 and is described in the Apple docs at New Features in Instruments 4.0   Let’s jump to the end and show you an example of what you can put up in your Instruments display:

FlagDisplay

Note the yellow flags above the trace.   These were generated in my code within a loop.    If you click on a flag you can see the text that I generated for the flag “Loop index 38” along with the source file, line number of the code generating the flag and the method  being executed.

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Using @autoreleasepool to reduce your memory footprint

When I was reviewing iOS memory management in the Apple documentation, I came across the section Use Local Autorelease Pool Blocks to Reduce Peak Memory Footprint

With the introduction of ARC (Automatic Reference Counting) memory management is largely taken care of for you.   There are still some cases you need to worry about though, including an increase in your memory footprint caused by creating temporary objects in a loop.

Consider the following code that allows me to populate some test data into the iOS Address Book.   Note that I inserted a sleep(4) after each iteration to more clearly show the memory allocation picture in steady state before a new iteration begins.

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Debugging memory leaks with Instruments and Heapshots

I was first introduced to Instruments in the CS193P course that I took over the past few months.   I found them to be invaluable for debugging memory leaks as I work on my Address Book iPhone app.

iOS Memory Instruments

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