#import <Foundation/Foundation.h>@interface QYPerson : NSObject{NSString *_name;
}//@property是编译指令，帮助直接生成setter和getter方法，以及成员变量
@property (readonly, nonatomic) NSString *identify;
@property (nonatomic) NSString *name;
@property (nonatomic) int age;
@property (nonatomic, getter=isMan) BOOL sex; // getter=isMan用来更改getter方法的名字，特别对于布尔值的一些属性这样改名字会有利用getter方法语义的理解，尽量不要该setter方法的名字// @property (nonatomic)int age;
// 中间的(nonatomic)是属性扩展，分为三类
// 内存相关的：strong assign copy weak retain
// 读写相关的：readonly readwrite(默认值)
// 性能相关的：nonaotmic aotmic@end

#import <Foundation/Foundation.h>@interface NSObject (BlackRule)- (void)laugh;@end

#import "NSObject+BlackRule.h"@implementation NSObject (BlackRule)- (void)laugh
{NSLog(@"?，你被潜规则了");
}@end

#import <Foundation/Foundation.h>@interface TestClass : NSObject@property (nonatomic, strong) NSString *name;- (void)doTthing;@end// 利用类别来拆分类的实现
@interface TestClass (TestCategory1)- (void)doTthing1;@end@interface TestClass (TestCategory2)- (void)doTthing2;@end@interface TestClass (TestCategory3)- (void)doTthing3;@end

        //@selector(destoriedLife)代表SEL method = @selector(destoriedLife);BOOL result = [ps respondsToSelector:method];if ([ps respondsToSelector:method]) {NSLog(@"执行destoriedLife");} else {NSLog(@"不能执行destoriedLife");}

#import <Foundation/Foundation.h>@protocol SecretProtocol <NSObject>+ (void)foo;- (void)phoneCall;
- (void)teakTea;@optional //@optional用来修饰协议里面的方法是否可选
- (void)goShopping;@required //@optional用来修饰协议里面的方法是必须实现的
- (void)meetting;
- (void)takeDinner;@end

#import <Foundation/Foundation.h>
#import "SecretProtocol.h"@interface Secrectary : NSObject <SecretProtocol>@end