类的声明和对象的创建、@property属性和点语法、类的继承

//类的声明@interface Person : NSObject{    //实例变量的声明    int identify;    int age;}//方法声明- (id) initWithAge:(int) _age identify:(int) _identify;- (int) getIdentify;- (int) getAge;- (void) setAge:(int) _age;@end//类的实现@implementation Person- (void) initWithAge:(int) _age identify _identify{    if (self = [super init]) {        age = _age;        identify = _identify;    }    return self;}- (int) getIdentify{    return identify;}- (int) getAge{    return age;}- (void) setAge: (int) _age{    age = _age;}@end对象的创建Person * person;    // nilperson = [[Person alloc] init]; //两个的方法，两个方法是否相同，与参数类型和返回值无关- (int) changed:(int) _age{}

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static关键字类体内的全局变量声明：static int gCount = 0; //这个值只有一份//解释属性nonatomic在@property()括号中，可以填写的属性：readwrite: 默认readonly: 只读，意味着没有set方法assign：默认，引用计数不增加retain:引用计数增加1原子性：actomic默认非原子性：nonatomicatomic是OC中的一种线程保护技术，是防止在未完成的时候，被另外一个线程使用。造成数据错误。点语法：person.myNumber = 100;NSLog(@"%d", person.myNumber);简化设置器@interface Person : NSObject@property(nonatomic) int myNumber;@end//实现部分@implementation Person@synthesize myNumber; //多个写多行，或者用逗号隔开也行，例如 @synthesize myNumber, age;@end以下是原始的方式@interface Person : NSObject{    int myNumber;     //实例变量}- (int) myNumber;- (void) setMyNumber:(int) _number;- (void) printfInfo;@end@implementation Person//get方法- (int) myNumber{    return myNumber;}//set方法- (void) setMyNumber:(int) _number{    myNumber = _number;}//打印本类的信息- (void) printfInfo{    NSLog(@"Person number is : %d", myNumber);}@end

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继承的书写@interface ClassB : ClassA@end@interface Rectangle : NSObject{    int width;    int height;}@Property (nonatomic) int width,height;- (int) area;- (int) perimeter;- (int) setWidth:(int) w andHeight:(int) h;@end@implementation Rectangle@synthesize width, height;- (int) area{    return width*height;}-(int)perimeter{    return (width + height) * 2;}- (void) setWidth: (int) w andHeight: (int) h{    width = w;    height = h;}@endmain方法中代码Rectangle *myRect = [[Rectangle alloc] init];[myRect setWidth:6 andHeight:7];NSLog(@"Rectangle: w = %d, h = %d", myRect.width, myRect.height);NSLog(@"Rectangle:area = %d perimeter = %d", [myRect area], [myRect perimeter] );方法的重载

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