Using NSLog to debug your iPhone application
I’ve done a lot of generative design in the last years. First in Macromedia Director and for the last two years I’ve been using Processing. Somewhere last week I started to play with the iPhone SDK and it’s quite easy to create small applications. I’ll probably create a small generative iPhone application in 2009 and write about what I’m learning right here.
Debugging Processing
Logging messages to the console in Processing is really easy. Just use the println(); function like in the example below.
int myNumber = 3;
String myText = "Dog";
println("My number is " + myNumber + " and my text is "
+ myText + ".");
This little snippet of code will log the text “My number is 3 and my text is dog.” to the console.
Debugging Objective-C
If you would convert this snippet code to Objective-C, you will get something like this:
int myNumber = 3;
NSString *myText = @"Dog";
NSLog("My number is %i and my text is %@.", myNumber,
myText);
The NSLog function replaces %i with myNumber and %@ with myText. %i and %@ are called format specifiers. They tell the NSLog function what type of variable myNumber and myText are. %i is used to represent an integer, %@ is used to represent an object. In this case myText is an NSString object.
Format Specifiers
And to finish this article i’ll give you a short list with the most common format specifiers you’ll need to debug your application.
- %i, %d signed integer
- %u unsigned integer
- %f float
- %@ object
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