Learning Objective-C
During the past week or so, I've been hacking away on iPhone native app dev. It's been a challenge, as I have very little experience with C, C++, much less obj-c. This entry is more a list of points that have helped me become comfortable than anything else - mostly gleaned from the docs put out by Apple.
File extensions
| .h | header files contain class, type, function, and constant declaration |
| .m | source files contain obj-c and c code |
use #import to include header files in source code - they will load files only once (as opposed to #include)
Strings
NSString* myString = @"My String";
Classes
defined in two parts:
interface (declares methods and instance variables, defines superclass)
@interface ClassName : ItsSuperclass
{
instance variable declarations
}
method declarations
@end
implementation (defines the class, contains the meat)
@implementation ClassName : ItsSuperclass
{
instance variable declarations
}
method definitions
@end
Methods
The names of methods that can be used by class objects, class methods, are preceded by a plus sign
+ alloc;
The methods that instances of a class can use, instance methods, are marked with a minus sign:
- (void)display;
Messaging
think of objects as actors
instead of calling an objects methods, send a message to an object requesting it to perform one of its methods and ask for a return
concentrate on behavior
to send a message:
[receiver message]
to recieve:
objc_msgSend(receiver, selector)
... and with arguments:
objc_msgSend(receiver, selector, arg1, arg2, ...)
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