5.25 类的引用与传值

1，类的引用
2，交叉引用与循环引用
3，传值的方式
4，数据持久化
5，NSUserDefaults的使用
6，单例

//  Observer.h#import <Foundation/Foundation.h>#import "Person.h"#import "ClassRoom.h"@interface Observer : NSObject@property (strong, nonatomic) Person        *per;@property (strong, nonatomic) ClassRoom     *classRoom;@property (strong, nonatomic) NSString      *keyword;@end

//  Observer.m//----属性传值//1.A.xx -> B.xx//2.A.xx -> C.xx//  C.xx -> B.xx//----初始化/代理  方法传值//----数据持久化（将任意数据归档之后，存放进本地文件）//关联式引用#import "Observer.h"#import "Computer.h"@implementation Observer- (instancetype)init{    self = [super init];    if (self) {        NSLog(@"observer init");        self.per = [[Person alloc]init];        self.per.keyword = self.keyword;//        _per.computer.keyword = _per.keyword;        _classRoom = [[ClassRoom alloc]init];        _classRoom.keyword = _per.keyword;        [self actionBegin];    }    return self;}- (void)actionBegin{    [_per walkToClassRoom:_classRoom];//    [_per walkToClassRoom:_classRoom];    NSLog(@"persons = %@",_classRoom.persons);}

//  ClassRoom.h#import <Foundation/Foundation.h>@interface ClassRoom : NSObject//给ClassRoom设置一个strong mutable的Array属性@property (strong, nonatomic) NSMutableArray *persons;//先初始化后使用@property (strong, nonatomic) NSString      *keyword;@end

//  ClassRoom.m#import "ClassRoom.h"@implementation ClassRoom- (instancetype)init{    self = [super init];    if (self) {        _persons = [NSMutableArray array];    }    return self;}@end

//  Person.h#import <Foundation/Foundation.h>@class Computer;@class ClassRoom;@interface Person : NSObject//{//    Computer *_computer;//}@property (strong, nonatomic) NSString      *name;@property (strong, nonatomic) Computer      *computer;//strong: 在使用属性的过程中，保证对象存在//retain:@property (strong, nonatomic) NSString      *keyword;//建立一个便利构造，通过电脑对象初始化Person+ (instancetype)personWithComputer:(Computer *)computer;- (void)walkToClassRoom:(ClassRoom *)classRoom;@end

//  Person.m////  --------   computer属性的存在时间//------------ person的存在时间#import "Person.h"#import "Computer.h"#import "ClassRoom.h"@implementation Person- (instancetype)init{    self = [super init];    if (self) {        NSLog(@"person init");        _computer = [[Computer alloc]init];//        _computer.keyword = self.delegate.keyword;        _computer.delegate = self;    }    return self;}+ (instancetype)personWithComputer:(Computer *)computer{    Person *per = [[self alloc]init];    per.computer = computer;    per.computer.delegate = per;//    per.point.x = 5;////    [per autorelease];//在方法中加入autorelease，使其内存管制无误，有且仅有一个    return [per autorelease];}- (void)walkToClassRoom:(ClassRoom *)classRoom{    [classRoom.persons addObject:self];}- (void)dealloc{    [_computer release];    [super dealloc];}@end

//  Computer.h#import <Foundation/Foundation.h>#import "Person.h"@interface Computer : NSObject@property (assign, nonatomic)Person     *delegate;//上一级//assign: 弱引用，不增加引用计数，保证对象即时释放//weak:@property (strong, nonatomic) NSString      *keyword;@end

//  Computer.m#import "Computer.h"@implementation Computer- (instancetype)init{    self = [super init];    if (self) {        NSLog(@"computer init");    }    return self;}//循环引用- (void)dealloc{    self.delegate = nil;//研究知识点：当owner是strong属性和assign属性的时候，分别有什么作用    [super dealloc];}@end

//  main.m#import <Foundation/Foundation.h>#import "Observer.h"#import "Person.h"#import "Computer.h"int main(int argc, const char * argv[]) {    @autoreleasepool {/*        Person *per = [[Person alloc]init];//        Computer *computer1 = [[Computer alloc]init];//        per.computer = [computer1 autorelease];//        [per release];        per.name = [NSString stringWithFormat:@"abc"];//retaincount = 2        per.name = [NSString stringWithFormat:@"bcd"];//2        per.name = nil;//没有        //对象的内存什么时候释放？        */        Observer *ob = [[Observer alloc]init];        NSArray *array = @[@"keyword"];        [array writeToFile:@"/Users/wangzheng/Desktop/classSeven.txt" atomically:YES];        NSArray *array1 = [NSArray arrayWithContentsOfFile:@"/Users/wangzheng/Desktop/classSeven.txt"];        NSLog(@"%@",array1);        //NSUserDefaults        [[NSUserDefaults standardUserDefaults]setObject:@"12345" forKey:@"account"];//将数据存入本地路径（移动设备路径）        BOOL succeed = [[NSUserDefaults standardUserDefaults]synchronize];   //获取到Document和Library        NSString *account = [[NSUserDefaults standardUserDefaults]objectForKey:@"account"];        NSLog(@"%@",account);  //数据持久化        //对象归档  NSKeyedArchiver NSKeyedUnarchiver       //网络请求  服务器       // 云  icloud        NSLog(@"Hello, World!");    }    return 0;}