{"id":11,"date":"2008-07-15T19:15:22","date_gmt":"2008-07-15T23:15:22","guid":{"rendered":"httpss:\/\/www.powenko.com\/blog\/?p=11"},"modified":"2008-07-19T13:54:21","modified_gmt":"2008-07-19T17:54:21","slug":"iphone-objective-c-learning-1-beginning","status":"publish","type":"post","link":"https:\/\/www.powenko.com\/wordpress\/?p=11","title":{"rendered":"iphone, objective-c, learning 1, Beginning"},"content":{"rendered":"

id<\/strong>
\nid anObject;
\nThis type is defined as a pointer to an object<\/a>\u2014in reality,
\nnil<\/strong>
\nNULL
\n[…]<\/strong>
\nobject messaging
\n[receiver message]
\n[myRect display];
\n[myRect setWidth:20.0];
\n[myRect setOrigin:30.0 :50.0]; \/\/ This is a bad example of multiple arguments
\n[receiver makeGroup:group, memberOne, memberTwo, memberThree];
\nBOOL isFilled = [myRect isFilled]; \/\/ if myRect filled returns YES,
\n[receiver makeGroup:group, memberOne, memberTwo, memberThree];
\n[myRect setPrimaryColor:[otherRect primaryColor]];<\/p>\n

.
\nDot Syntax<\/strong>
\nmyInstance.value = @”New value”; \/\/[myInstance setValue:@”New value”];
\nNSLog(@”myInstance value: %@”, myInstance.value); \/\/NSLog(@”myInstance value: %@”, [myInstance value]);<\/p>\n

string<\/strong><\/p>\n

NSString*  myString = @\"My String\\n\";\r\nNSString*  anotherString = [NSString stringWithFormat:@\"%d %s\", 1, @\"String\"];\r\n\r\n\/\/ Create an Objective-C string from a C string\r\nNSString*  fromCString = [NSString stringWithCString:\"A C string\" encoding:NSASCIIStringEncoding];<\/pre>\n
Listing 1-1  Accessing properties using the dot syntax<\/strong>
\nGraphic *graphic = [[Graphic alloc] init];<\/p>\n
NSColor *color = graphic.color;
\nCGFloat xLoc = graphic.xLoc;
\nBOOL hidden = graphic.hidden;
\nint textCharacterLength = graphic.text.length;<\/p>\n
if (graphic.textHidden != YES) {
\ngraphic.text = @”Hello”;
\n}
\ngraphic.bounds = NSMakeRect(10.0, 10.0, 20.0, 120.0)
\n Listing 1-2  Accessing properties using accessor methods, as same as Listing 1-1<\/strong>
\nGraphic *graphic = [[Graphic alloc] init];<\/p>\n
NSColor *color = [graphic color];
\nCGFloat xLoc = [graphic xLoc];
\nBOOL hidden = [graphic hidden];
\nint textCharacterLength = [[graphic text] length];<\/p>\n
if ([graphic isTextHidden] != YES) {
\n[graphic setText:@”Hello”];
\n}
\n[graphic setBounds:NSMakeRect(10.0, 10.0, 20.0, 120.0)];<\/p>\n
Listing 1-3<\/strong>
\nNSMutableData *data = [NSMutableData dataWithLength:1024];
\ndata.length += 1024;   \/\/[data setLength:[data length] + 1024];
\ndata.length *= 2;   \/\/[data setLength:[data length] * 2];
\ndata.length \/= 4;   \/\/[data setLength:[data length] \/ 4];<\/p>\n
 Listing 1-4<\/strong>
\n\/\/ each member of the path is an object
\nx = person.address.street.name; \/\/ x = [[[person address] street] name];<\/p>\n
\/\/ the path contains a C struct
\n\/\/ will crash if window is nil or -contentView returns nil
\ny = window.contentView.bounds.origin.y;  \/\/ y = [[window contentView] bounds].origin.y;<\/p>\n
\/\/ an example of using a setter….
\nperson.address.street.name = @”Oxford Road”; \/\/ [[[person address] street] setName: @”Oxford Road”];<\/p>\n
Self<\/strong>
\nself.age = 10;<\/p>\n
Key-value coding (KVC)<\/strong>
\n Sample: define a class<\/em>
\n@interface MyClass
\n@property NSString *stringProperty;
\n@property NSInteger integerProperty;
\n@property MyClass *linkedInstance;
\n@end<\/p>\n
Used the class in below, sample 1<\/em>
\nMyClass *myInstance = [[MyClass alloc] init];
\nNSString *string = [myInstance valueForKey:@”stringProperty”];
\n[myInstance setValue:[NSNumber numberWithInt:2] forKey:@”integerProperty”];<\/p>\n
sample2<\/em><\/span>
\nMyClass *anotherInstance = [[MyClass alloc] init];
\nmyInstance.linkedInstance = anotherInstance;
\nmyInstance.linkedInstance.integerProperty = 2;<\/p>\n
 sample3: This has the same result as:<\/em><\/span>
\nMyClass *anotherInstance = [[MyClass alloc] init];
\nmyInstance.linkedInstance = anotherInstance;
\n[myInstance setValue:[NSNumber numberWithInt:2] forKeyPath:@”linkedInstance.integerProperty”];
\naVariable = anObject.aProperty;
\nanObject.name = @”New Name”;
\nxOrigin = aView.bounds.origin.x;
\nNSInteger i = 10;
\nanObject.integerProperty = anotherObject.floatProperty = ++i;<\/p>\n
Class<\/h3>\n
\"\"<\/a><\/p>\n
Rectangle *myRect;
\nGraphic *myRect;<\/p>\n
if ( [anObject isMemberOfClass:someClass] )
\nif ( [anObject isKindOfClass:someClass] )<\/p>\n
Class Objects<\/strong>
\nint versionNumber = [Rectangle version];
\nid aClass = [anObject class];
\nid rectClass = [Rectangle class];
\nClass aClass = [anObject class];
\nClass rectClass = [Rectangle class];<\/p>\n
Creating Instances<\/strong>
\nid  myRect;
\nmyRect = [Rectangle alloc];  \/\/ dynamically allocates memor
\nmyRect = [[Rectangle alloc] init];  \/\/same as,  myRect = [Rectangle alloc];
\n[myMatrix setCellClass:[NSButtonCell class]];<\/p>\n
Class Object<\/h3>\n
\"\"<\/p>\n
create Class Object <\/strong>
\nint MCLSGlobalVariable;
\n@implementation MyClass
\n\/\/ implementation continues<\/p>\n
static MyClass *MCLSSharedInstance;
\n@implementation MyClass
\n+ (MyClass *)sharedInstance
\n{
\n\/\/ check for existence of shared instance
\n\/\/ create if necessary
\nreturn MCLSSharedInstance;
\n}
\n\/\/ implementation continues<\/p>\n
 Initializing<\/strong>
\n+ (void)initialize
\n{
\nstatic BOOL initialized = NO;
\nif (!initialized) {
\n\/\/ Perform initialization here.
\n…
\ninitialized = YES;
\n}
\n}<\/p>\n
Class Names in Source Cod<\/strong>
\nRectangle *anObject;
\nif ( [anObject isKindOfClass:[Rectangle class]] )
\nNSString *className;
\nif ( [anObject isKindOfClass:NSClassFromString(className)] )
\nDefining a Class<\/strong><\/p>\n
Class Interface<\/strong>
\nsolution 1: <\/em>
\n#import “ItsSuperclass.h”<\/p>\n
@interface ClassName : ItsSuperclass
\n{
\ninstance variable declarations
\n}
\nmethod declarations
\n@end<\/p>\n
solution 2:<\/em>
\n#import “ClassName.h”<\/p>\n
@implementation ClassName
\nmethod definitions
\n@end<\/p>\n
+ alloc{    …}
\n– (BOOL)isfilled{    …}
\n– (void)setFilled:(BOOL)flag{    …}<\/p>\n
#import
\n– getGroup:group, …
\n{  va_list ap;
\nva_start(ap, group);
\n}<\/p>\n
Referring to Instance Variables<\/strong>
\n– (void)setFilled:(BOOL)flag
\n{
\nfilled = flag;
\n…
\n}<\/p>\n
@interface Sibling : NSObject
\n{
\nSibling *twin;
\nint gender;
\nstruct features *appearance;
\n}<\/p>\n
– makeIdenticalTwin
\n{
\nif ( !twin ) {
\ntwin = [[Sibling alloc] init];
\ntwin->gender = gender;
\ntwin->appearance = appearance;
\n}
\nreturn twin;
\n}<\/p>\n
– (BOOL)isFilled
\n{
\nreturn filled;
\n}<\/p>\n
Referring to Other Classes<\/strong>
\n@class Rectangle, Circle;
\n– (void)setPrimaryColor:(NSColor *)aColor;<\/p>\n\n\n\n\n\n\n\n
Directive<\/th>\nMeaning<\/th>\n<\/tr>\n
@private<\/code><\/td>\nThe instance variable<\/a> is accessible only within the class that declares it.<\/td>\n<\/tr>\n
@protected<\/code><\/td>\nThe instance variable is accessible within the class that declares it and within classes that inherit it.<\/td>\n<\/tr>\n
@public<\/code><\/td>\nThe instance variable is accessible everywhere.<\/td>\n<\/tr>\n
@package<\/code><\/td>\nOn 64-bit, an @package<\/code> instance variable acts like @public<\/code> inside the image that implements the class, but @private<\/code> outside. This is analogous to private_extern<\/code> for variables and functions. Any code outside the class implementation\u2019s image that tries to use the instance variable will get a link error. This is most useful for instance variables in framework classes, where @private<\/code> may be too restrictive but @protected<\/code> or @public<\/code> too permissive.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
@interface Worker : NSObject
\n{
\nchar *name;
\n@private
\nint age;
\nchar *evaluation;
\n@protected
\nid job;
\nfloat wage;
\n@public
\nid boss;
\n}<\/p>\n
– promoteTo:newPosition
\n{
\nid old = job;
\njob = newPosition;
\nreturn old;
\n}<\/p>\n
Worker *ceo = [[Worker alloc] init];
\nceo->boss = nil;<\/p>\n
Categories and Extensions<\/h3>\n
#import “ClassName+CategoryName.h”<\/p>\n
@implementation ClassName ( CategoryName )
\n\/\/ method definitions
\n@end<\/p>\n
Extensions<\/strong>
\n@interface MyObject : NSObject
\n{    NSNumber *number;
\n}
\n– (NSNumber *)number;
\n@end<\/p>\n
@interface MyObject (Setter)
\n– (void)setNumber:(NSNumber *)newNumber;
\n@end<\/p>\n
@implementation MyObject
\n– (NSNumber *)number
\n{    return number;
\n}
\n@end<\/p>\n
@interface MyObject : NSObject
\n{   NSNumber *number;
\n}
\n– (NSNumber *)number;
\n@end<\/p>\n
@interface MyObject ()
\n– (void)setNumber:(NSNumber *)newNumber;
\n@end<\/p>\n
@implementation MyObject
\n– (NSNumber *)number
\n{    return number;
\n}
\n– (void)setNumber(NSNumber *)newNumber
\n{    number = newNumber;
\n}
\n@end
\nDeclared Properties<\/strong>
\nDeclaring properties in a class<\/em>
\n\/\/ MyClass.h
\n@interface MyClass : NSObject
\n{
\nNSString *value;
\nNSTextField *textField;
\n@private
\nNSDate *lastModifiedDate;
\n}
\n@property(copy, readwrite) NSString *value;
\n@property(retain) IBOutlet NSTextField *textField;
\n@end<\/p>\n
\/\/ MyClass.m
\n\/\/ Class extension to declare private property
\n@interface MyClass ()
\n@property(retain) NSDate *lastModifiedDate;
\n@end<\/p>\n
@implementation MyClass
\n@synthesize value;
\n@synthesize textField;
\n@synthesize lastModifiedDate;
\n\/\/ implementation continues
\n@end<\/p>\n
Using Properties<\/strong>
\n– (NSString *)name;
\n– (void)setName:(NSString *)newName;  \/\/ same as, @property NSString *name;<\/p>\n
@interface MyClass : NSObject
\n{    NSString *value;
\n}
\n@property(copy, readwrite) NSString *value;
\n@end<\/p>\n
@implementation MyClass
\n@synthesize value;
\n@end<\/p>\n
@interface MyClass : NSObject
\n{
\nNSString *value;
\n}
\n@property(copy, readwrite) NSString *value;
\n@end<\/p>\n
\/\/ assume using garbage collection
\n@implementation MyClass
\n@dynamic value;
\n– (NSString *)value {
\nreturn value;
\n}
\n– (void)setValue:(NSString *)newValue {
\nif (newValue != value) {
\nvalue = [newValue copy];
\n}
\n}
\n@end<\/p>\n
getter=getterName, setter=setterName<\/em>
\ngetter= and setter= specify respectively the names of get and set accessors for the property. The getter must return a type matching the property\u2019s type and take no arguments. The setter method must take a single argument of a type matching the property\u2019s type and must return void.<\/p>\n
readonly<\/em>
\nIndicates that the property is read-only. The default is read\/write.<\/p>\n
readwrite<\/em>
\nIndicates that the property should be treated as read\/write. This is the default.<\/p>\n
assign<\/em>
\nSpecifies that the setter uses simple assignment. This is the default.<\/p>\n
retain<\/em>
\nSpecifies that retain should be invoked on the object upon assignment. (The default is assign.)<\/p>\n
copy<\/em>
\nSpecifies that a copy of the object should be used for assignment. (The default is assign.)<\/p>\n
nonatomic<\/em>
\nSpecifies that accessors are non-atomic. By default, accessors are atomic.( There is no keyword to denote atomic.)<\/p>\n
Property Re-declaration<\/strong>
\n@interface MyObject : NSObject
\n{   NSString *language;
\n}
\n@property (readonly, copy) NSString *language;
\n@end<\/p>\n
\/\/ private implementation file
\n@interface MyObject ()
\n@property (readwrite, copy) NSString *language;
\n@end<\/p>\n
@implementation MyObject
\n@synthesize language;
\n@end<\/p>\n
@property (nonatomic, copy) NSString *string;
\n-(void)setString:(NSString *)newString
\n{
\nif (string != newString) {
\n[string release];
\nstring = [newString copy];
\n}
\n}<\/p>\n
@interface MyClass : NSObject
\n{
\nNSMutableArray *myArray;
\n}
\n@property (nonatomic, copy) NSMutableArray *myArray;
\n@end<\/p>\n
@implementation MyClass<\/p>\n
@synthesize myArray;<\/p>\n
– (void)setMyArray:(NSMutableArray *)newArray
\n{
\nif (myArray != newArray) {
\n[myArray release];
\nmyArray = [newArray mutableCopy];
\n}
\n}<\/p>\n
@end<\/p>\n
Property Declaration<\/strong>
\n@interface MyClass : NSObject
\n{
\nNSString *value;
\n}
\n@property(copy, readwrite) NSString *value;
\n@end<\/p>\n
\/\/ assume using garbage collection
\n@implementation MyClass
\n@dynamic value;<\/p>\n
– (NSString *)value {
\nreturn value;
\n}<\/p>\n
– (void)setValue:(NSString *)newValue {
\nif (newValue != value) {
\nvalue = [newValue copy];
\n}
\n}
\n@end<\/p>\n
@interface MyClass : NSObject
\n{
\nNSMutableArray *myArray;
\n}
\n@property (nonatomic, copy) NSMutableArray *myArray;
\n@end<\/p>\n
@implementation MyClass<\/p>\n
@synthesize myArray;<\/p>\n
– (void)setMyArray:(NSMutableArray *)newArray
\n{
\nif (myArray != newArray) {
\n[myArray release];
\nmyArray = [newArray mutableCopy];
\n}
\n}<\/p>\n
@end<\/p>\n
Sample Class 1:<\/strong>
\n@interface MyClass : NSObject
\n{
\n\tint \t\tcount;
\n\tid  \t\tdata;
\n\tNSString*\tname;
\n}
\n-(id)initWithString: (NSString*) aName;
\n+(MyClass*)createMyClassWithString: (NSString*)aName;
\n@end<\/p>\n
@implementation MyClass
\n– (id)initWithString:(NSString *) aName
\n{
\n    if (self = [super init]) {
\n        count count = 0;
\n        data = nil;
\n        name = [aName copy];
\n        return self;
\n    }
\n}<\/p>\n
+ (MyClass *)createMyClassWithString: (NSString *) aName
\n{
\n    return [[[self alloc] initWithString:aName] autorelease];
\n}
\n@end<\/p>\n
reference:<\/strong>
\nhttpss:\/\/developer.apple.com\/iphone\/library\/documentation\/Cocoa\/Conceptual\/ObjectiveC\/Introduction\/chapter_1_section_1.html
\nObjective begin tutor
\nhttpss:\/\/freeborn.wordpress.com\/2008\/03\/10\/iphone-developmenet-where-to-start\/
\nhttpss:\/\/theocacao.com\/document.page\/510<\/p>\n","protected":false},"excerpt":{"rendered":"
id id anObject; This type is defined as a pointer to an […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[],"class_list":["post-11","post","type-post","status-publish","format-standard","hentry"],"_links":{"self":[{"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/11"}],"collection":[{"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=11"}],"version-history":[{"count":0,"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/11\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=11"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.powenko.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}