See Also

• Great tutorial here: http://www.cocoadevcentral.com/d/learn_objectivec/

Syntax

Methods

Methods called on objects

• [object method];
• [object method:input];
• output = [object method:input];

Multi-param methods

• BOOL result = [myData writeToFile:@"/tmp/log.txt" atomically:NO];
  Declared in the header as:
  -(BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile;

Class methods

• NSString* some_str = [NSString string]; -- make a string
• id some_object = [NSString string];
  (id is 'mother of all objects')

Method parameters that are methods

• rather than string blah* = new String(make_format()), do
  NSString* some_str = [NSString stringWithFormat:[prefs format]];

Members and Accessors

• all private by default

Classic Style (Obj-C 1.0)

• Set: [thing setName:@"name for thing"];
• Get: out = [thing name]; - NOTE: name is actually a METHOD. Obj-C convention - not named getName

Dot Style (Obj-C 2.0)

• thing.name = @"name for thing";
• out = thing.name;
• NOTE: - use dot style only for getters and setters

Making Objects

Automatic style:

• NSString* string = [NSString string];

Manual Style:

• = NSString* string = [[NSString alloc] init];=
  Like: StringClass* string = StringClass.factory();
string.init();
• Or, NSNumber* val = [[NSNumber alloc] initWithFloat:1.0];
• Later, you must do [string release];

Defining Objects

#import <Cocoa/Cocoa.h>  // import is nice; won't let you import file more than once
@interface Name : NSObject {
   NSString* first;
   NSString* last;

// 'get' accessors; '-' means instance method.  Assumed return type is 'id'
- first; 
- last; 

// can alternatively specify return type
- (NSString*) first

// 'set' accessors
- (void) setFirst: (NSString*)input;

+ makeMatt; // '+' means class method

}
@end

Implementing Objects

@implementation Name

- (NSString*) first {  return first; }

- (void) setFirst: (NSString*)input
{
// without GC
   [first autorelease];   
// also, just 'release' - immediate free - 'autorelease' keeps at least till func over
   first = [input retain];

// alternatively, with GC
   first = input;
}


- (id) init
{
   if ( self = [super init] ) // let superclass do its init, = succeeds if init was ok
   {
      [ self setFirst:@"Joe"];
      [ self setLast:@"Schmoe"];
   }
   return self;  // MSW: is 'self' == 'this' ?
}

- (void) dealloc  // or use 'finalize' if no GC
{
   [first release];   // don't need autorelease; release a bit faster
   [last release];
   [super dealloc];
}
@end

-- MattWalsh - 03 Sep 2009