一、主要属性介绍
1、自动合成setter、getter方法
1)、接口部分@property指定属性 2)、实现部分@synthesize
如果
@syntheszie widows = _windows
这里成员变量名是_windows,而不是windows
2、atomic(nonatomic)
这里主要是指存取方法为原子操作，实现线程安全，atomic是默认，保证线程安全，但是会导致性能降低，单线程我们一般考虑nonatomic
3、copy
用这个修饰了属性名，把副本值设置给类的属性，如果赋值的副本发生改变，但是类部的属性值不会改变
4、getter、setter
如果(getter = ff1, setter = ff2)，会把默认的getter方法改为ff1, 会把默认setter方法改为ff2,我们调用的时候就是[对象 ff1]、[对象 ff2]
5、readonly、readwirte
readonly是指系统指合成getter方法，不合成setter方法
readwirte是默认的，都合成
6、retain
使用retain指示定义属性时，当莫个对象赋值给属性时，该属性原来所引用的对象引用计数减1，被赋值对象的引用计数加1
当一个对象的引用计数大于1时，该对象不该被回收。
7、strong、weak
strong:指被赋值对象持有强引用，不会自动回收
weak:使用弱引用指向被赋值对象，该对象可能被回收
二、测试demo
User.h
#ifndef User_h #define User_h #import <Foundation/Foundation.h> @interface User : NSObject @property (nonatomic) NSString *name; @property (nonatomic) NSString *city; @property (nonatomic, copy) NSString *add; @property NSString *pass; @property NSDate *birth; @property NSDate *birth1; @end #endif /* User_h */
User.m
#import <Foundation/Foundation.h> #import "User.h" @implementation User @synthesize name = _name; @synthesize pass; @synthesize birth; -(void) setName:(NSString *)name { self->_name = [NSString stringWithFormat:@"hello%@", name]; } @end
main.m文件
#import <UIKit/UIKit.h> #import "AppDelegate.h" #import "Person.h" #import "Apple.h" #import "User.h" #import "Args.h" #import "KVCPerson.h" int main(int argc, char * argv[]) { @autoreleasepool { User *user = [User new]; NSMutableString *name = [NSMutableString stringWithString:@"chencaifeng"]; NSMutableString *city = [NSMutableString stringWithString:@"hunan"]; NSMutableString *addr = [NSMutableString stringWithString:@"luyunlu"]; [user setName:name]; [user setCity:city]; [user setAdd:addr]; [user setPass:@"hello"]; [user setBirth:[NSDate date]]; NSLog(@"name is %@, and pass is %@, birth is%@, city is%@, add is %@", [user name], [user pass], [user birth], [user city], [user add]); //我们把setName函数重写了，虽然name后面追加了字符串，但是后面打印值没有改变 [name appendString:@"chenyu"]; //由于这里属性没有加copy，city后面追加了字符串，所以后面打印也变了 [city appendString:@"changsha"]; //由于这里属性加了copy,由于这个addr后面值追加了，所以后面打印不会改变 [addr appendString:@"kanyunlu"]; NSLog(@"name is %@, and pass is %@, birth is%@, city is%@, add is %@", [user name], [user pass], [user birth], [user city], [user add]); //这里是用.操作 user.add = @"hello"; NSLog(@"user add is %@", user.add); } }
三、运行结果
name is hellochencaifeng, and pass is hello, birth isFri Jul 6 19:51:04 2018, city ishunan, add is luyunlu
name is hellochencaifeng, and pass is hello, birth isFri Jul 6 19:51:04 2018, city ishunanchangsha, add is luyunlu
user add is hello
