Objective C

Introduction

Objective-C is a strict superset of C. It adds in the concept of messaging:

[myArray insertObject:anObject atIndex:0];

File management

• .h is for header files, containing class, type, function, and constant declarations.
• .m is for source files, containing implementations.
• Use #import to access declarations from other files.

Memory management

If you create a variable of a non-builtin-type (not int or float), then you need to release it when you're done with it:

[tempName release];

Call this within scope for a temporary variable, or in the class's dealloc method for an instance variable.

Classes

Interface declaration in MyClass.h:

#import "MySuperClass.h"

@interface MyClass : MySuperClass {
    // instance variables
}
+classMethod1;  // void return type
+(return_type)classMethod2;  // takes no parameter
+(return_type)classMethod3:(param_type)paramName;
-(return_type)instanceMethod:(param_type)param1 :(param_type)param2;
-(return_type)instanceMethodWithNamedParameter:(param_type)param1 namedParameter:(param_type)param2;

@end

Another interface declaration in MyOtherClass.h:

@interface MyOtherClass : NSObject
{
    int         count;  // strongly typed
    id          data;   // weakly typed - allows assignment of an arbitrary object
    NSString*   name;  // strongly typed
}
- (id)initWithString:(NSString*)aName;              // instance method
+ (MyOtherClass)createWithString:(NSString*)aName;  // class method
@end

An implementation in MyOtherClass.m:

@implementation MyOtherClass

- (id)initWithString:(NSString *)aName
{
    if (self = [super init]) {
        name = [aName copy];
    }
    return self;
}

+ (MyOtherClass *)createWithString: (NSString *)aName
{
    return [[[self alloc] initWithString:aName] autorelease];
}
@end

Class properties with getters and setters

In the .h file:

@property BOOL flag;
@property (copy) NSString *nameObject;  // Copy the object during assignment.
@property (readonly) UIView *rootView;  // Declare only a getter method.

Generate the appropriate getters and setters in the .m file with synthesize:

@synthesize flag, nameObject, rootView;

Strings

String literals must be preceded by an @ sign:

NSString *myString = @"My String\n";
NSString *anotherString = [NSString stringWithFormat:@"%d %s", 1, @"String"];

Resources

http://www.devworld.apple.com/iphone/library/referencelibrary/GettingStarted/Learning_Objective-C_A_Primer/

http://www.devworld.apple.com/iphone/library/documentation/Cocoa/Conceptual/ObjectiveC/Introduction/introObjectiveC.html

http://www.devworld.apple.com/iphone/library/documentation/Cocoa/Conceptual/ObjectiveC/Articles/ocLanguageSummary.html

http://en.wikipedia.org/wiki/Objective-C