iOS OC08,09_内存管理

Posted 2020-09-30 cxchanpin

//管理内存有三种方式,
    //1.是垃圾回收,java常见的管理内存的方法,系统来检測对象是否被使用,是否被释放
    //2.MRC手动管理引用计数,ios管理内存的方式,程序猿通过手动的方式来管理对象是否被释放
    //3.ARC自己主动管理引用计数,基于MRC,系统自己主动的管理内存,以后我们还是先使用MRC,培养管理内存的习惯

//
//  Girl.h
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import <Foundation/Foundation.h>
//1.声明协议
@protocol GirlDelegate <NSObject>

@required
-(void)married;

@optional
-(void)cook;
@end

@interface Girl : NSObject
//2.声明代理人属性
@property(nonatomic,assign)id<GirlDelegate>delegate;

-(void)getMarry;


@end







//
//  Girl.m
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import "Girl.h"

@implementation Girl
-(void)getMarry{
    [self.delegate cook];
}

@end

//
//  Boy.h
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Girl.h"
@interface Boy : NSObject<GirlDelegate,NSCopying>

-(void)dealloc;

+(Boy*)boy;

@property(nonatomic,retain)NSString *name;
@property(nonatomic,copy)NSString *hobby;
@property(nonatomic,retain)Girl *girls;

//自己定义的初始化方法
-(instancetype)initWithName:(NSString *)name
                      hobby:(NSString *)hobby;
+(Boy *)boyWithName:(NSString *)name
              hobby:(NSString *)hobby;

@end




//
//  Boy.m
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import "Boy.h"

@implementation Boy


-(void)cook{
    NSLog(@"做饭吃");
}

-(void)dealloc{
    NSLog(@"对象被释放了");

    //把成员变量全部+1操作全部减去
    [_name release];
    [_girls release];
    [_hobby release];

    [super dealloc];
}


+(Boy*)boy{
    Boy *b=[[Boy alloc] init];
    return [b autorelease];
}
//id是void *
//id是泛型指针,能够用在不论什么方法中,可是instancetype代表实例类型,用在自己定义初始化方法,便利构造器作为返回值类型使用,标识方法会返回一个对象回去
//-(instancetype)init{
//   Boy *b=[[Boy alloc] init];
//    return [b autorelease];
//}

- (id)copyWithZone:(NSZone *)zone{
    Boy *b=[Boy allocWithZone:zone];

    b.hobby=_hobby;
    b.name=_name;
    return b;

}



-(instancetype)initWithName:(NSString *)name
                      hobby:(NSString *)hobby{
    [super self];
    if (self) {
        self.name=name;   //从直接赋值变成方法赋值
        _hobby=hobby;
    }return self;
}


+(Boy *)boyWithName:(NSString *)name
              hobby:(NSString *)hobby{
    Boy *b=[[Boy alloc] initWithName:name hobby:hobby];
    //写便利构造器最后别忘了autorelease
    return [b autorelease];
}


-(void)setName:(NSString *)name{
    if(_name!=name);
    [_name release];
    _name=[name retain];
}



@end

对象被创建出来之后他的引用计数retainCount就变成1

Boy *boy=[[Boy alloc] init];
NSLog(@"%ld",boy.retainCount);

结果

2015-07-27 17:47:40.331 OC08,09_内存管理[1562:152231] 1

//对对象的引用计数进行+1的操作

// //retain:对对象的引用计数进行+1

Boy *boy=[[Boy alloc] init];
NSLog(@"%ld",boy.retainCount);
[boy retain];
NSLog(@"%ld",boy.retainCount);
[boy retain];
[boy retain];
NSLog(@"%ld",boy.retainCount);

结果

2015-07-27 17:50:13.304 OC08,09_内存管理[1571:153537] 1
2015-07-27 17:50:13.305 OC08,09_内存管理[1571:153537] 2
2015-07-27 17:50:13.305 OC08,09_内存管理[1571:153537] 4

//release:对对象的引用计数进行-1的操作

[boy release];
NSLog(@"%ld",boy.retainCount);
[boy release];
[boy release];
[boy release];
NSLog(@"%ld",boy.retainCount);

结果

2015-07-27 17:54:44.714 OC08,09_内存管理[1580:155505] 1
2015-07-27 17:54:44.715 OC08,09_内存管理[1580:155505] 对象被释放了
2015-07-27 17:54:44.715 OC08,09_内存管理[1580:155505] 1

凝视

//     //假设多次对对象进行释放,会造成过度释放,过度释放也是最常见的内存问题(+1次数小于-1次数)
//    //[boy release];
//    //当对象的引用计数1->0时,会自己主动调用dealloc方法,dealloc才是相应对象释放的方法
//当对象调用release的时候,他的引用计数是1,这个对象就不再对他的引用计数进行-1操作,而是直接调用dealloc方法,所以我们在訪问对象引用计数还是1

几个不同类型retain值

NSArray *[email protected][@"1",@"2",@"3",@"4"];
NSLog(@"%ld",arr.retainCount);

NSString *[email protected]"1111";
NSLog(@"%ld",str.retainCount);

NSMutableString *str2=[NSMutableString stringWithString:@"111111"];
NSLog(@"%ld",str2.retainCount);

NSDictionary *[email protected]{@"1":@"2",@"3":@"4"};
NSLog(@"%ld",dic.retainCount);
NSLog(@"%p",str);
NSLog(@"%p",str2);

结果

2015-07-27 17:56:31.134 OC08,09_内存管理[1587:156279] 1
2015-07-27 17:56:31.134 OC08,09_内存管理[1587:156279] -1
2015-07-27 17:56:31.135 OC08,09_内存管理[1587:156279] 1
2015-07-27 17:56:31.135 OC08,09_内存管理[1587:156279] 1
2015-07-27 17:56:31.135 OC08,09_内存管理[1587:156279] 0x100002130
2015-07-27 17:56:31.135 OC08,09_内存管理[1587:156279] 0x100112ac0

凝视

NSString 的对象在全局静态区,他的引用计数是-1,代表正整数的最大值,其它的对象都在堆区,

Boy *boy=[[Boy alloc] init];
[boy retain];
[boy retain];
NSLog(@"%ld",boy.retainCount);
//release立即会把对象的引用计数-1,可是autorelease会延迟对对象的计数-1
[boy release];
NSLog(@"%ld",boy.retainCount);
[boy autorelease];
NSLog(@"%ld",boy.retainCount);
//自己主动释放池
//仅仅要对象用autorelease释放会把对象放入到系统的自己主动释放池中,等出了池子范围,对象引用计数自己主动-1,这个相当于java的垃圾回收,对象释放由系统来管理
 @autoreleasepool {
 [boy autorelease];
 NSLog(@"%ld",boy.retainCount);
 }NSLog(@"%ld",boy.retainCount);

结果

2015-07-27 19:00:44.667 OC08,09_内存管理[1602:162429] 3
2015-07-27 19:00:44.668 OC08,09_内存管理[1602:162429] 2
2015-07-27 19:00:44.668 OC08,09_内存管理[1602:162429] 2
2015-07-27 19:00:44.668 OC08,09_内存管理[1602:162429] 2
2015-07-27 19:00:44.668 OC08,09_内存管理[1602:162429] 1

// 内存管理原则:加多少减多少,加减做到平衡,减多了过度释放,降低了没有得到释放

//对象的全部权:拥有全部权的对象能够对他进行release

Boy *b=[Boy boy];
[b retain];
NSLog(@"%ld",b.retainCount);
[b release];

结果

2015-07-27 19:05:11.838 OC08,09_内存管理[1610:164027] 2

 //便利构造器在返回对象的时候会加上一个autorelease,所以用便利构造器创建对象不须要对内存进行管理
NSArray *arr1=[[NSArray alloc] initWithObjects:@"1",@"2", nil];
NSArray *arr2=[NSArray arrayWithObjects:@"1",@"2",nil];
[arr1 release];

    NSArray *[email protected][@"1",@"2",@"3",@"4"];
    NSArray *newArr=[NSArray arrayWithArray:arr];
    NSLog(@"%@",newArr);
    NSLog(@"%ld",arr.retainCount);
    NSLog(@"%ld",newArr.retainCount);

结果

2015-07-27 19:07:04.008 OC08,09_内存管理[1624:164855] (
    1,
    2,
    3,
    4
)
2015-07-27 19:07:04.009 OC08,09_内存管理[1624:164855] 1
2015-07-27 19:07:04.010 OC08,09_内存管理[1624:164855] 1

//把一个不可变的变成可变的

NSArray *[email protected][@"1",@"2",@"3",@"4"];
NSMutableArray *arr1=[NSMutableArray arrayWithArray:arr];

NSMutableArray *arr2=[arr mutableCopy];
[arr2 addObject:@"5"];
NSLog(@"%@",arr2);


NSDictionary *[email protected]{@"1":@"2",@"3":@"4"};
NSMutableDictionary *dic1=[dic mutableCopy];
NSLog(@"%@",dic1);

结果

2015-07-27 19:08:34.111 OC08,09_内存管理[1633:165509] (
    1,
    2,
    3,
    4,
    5
)
2015-07-27 19:08:34.112 OC08,09_内存管理[1633:165509] {
    1 = 2;
    3 = 4;
}

凝视

//系统的类要是实现copy功能,必须先签订拷贝NSCopying协议,然后实现相应的方法
//不可变的数组字典能够通过mutableCopy转换成可变的数组字典
//mutableCopy出来的对象可变,copy是不可变的

举例

Girl Boy文件

//
//  Girl.h
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import <Foundation/Foundation.h>
//1.声明协议
@protocol GirlDelegate <NSObject>

@required
-(void)married;

@optional
-(void)cook;
@end

@interface Girl : NSObject
//2.声明代理人属性
@property(nonatomic,assign)id<GirlDelegate>delegate;

-(void)getMarry;


@end


//
//  Girl.m
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import "Girl.h"

@implementation Girl
-(void)getMarry{
    [self.delegate cook];
}

@end




//
//  Boy.h
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Girl.h"
@interface Boy : NSObject<GirlDelegate,NSCopying>

-(void)dealloc;

+(Boy*)boy;

@property(nonatomic,retain)NSString *name;
@property(nonatomic,copy)NSString *hobby;
@property(nonatomic,retain)Girl *girls;

//自己定义的初始化方法
-(instancetype)initWithName:(NSString *)name
                      hobby:(NSString *)hobby;
+(Boy *)boyWithName:(NSString *)name
              hobby:(NSString *)hobby;

@end





//
//  Boy.m
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import "Boy.h"

@implementation Boy


-(void)cook{
    NSLog(@"做饭吃");
}

-(void)dealloc{
    NSLog(@"对象被释放了");

    //把成员变量全部+1操作全部减去
    [_name release];
    [_girls release];
    [_hobby release];

    [super dealloc];
}


+(Boy*)boy{
    Boy *b=[[Boy alloc] init];
    return [b autorelease];
}
//id是void *
//id是泛型指针,能够用在不论什么方法中,可是instancetype代表实例类型,用在自己定义初始化方法,便利构造器作为返回值类型使用,标识方法会返回一个对象回去
//-(instancetype)init{
//   Boy *b=[[Boy alloc] init];
//    return [b autorelease];
//}

- (id)copyWithZone:(NSZone *)zone{
    Boy *b=[Boy allocWithZone:zone];

    b.hobby=_hobby;
    b.name=_name;
    return b;

}



-(instancetype)initWithName:(NSString *)name
                      hobby:(NSString *)hobby{
    [super self];
    if (self) {
        self.name=name;   //从直接赋值变成方法赋值
        _hobby=hobby;
    }return self;
}


+(Boy *)boyWithName:(NSString *)name
              hobby:(NSString *)hobby{
    Boy *b=[[Boy alloc] initWithName:name hobby:hobby];
    //写便利构造器最后别忘了autorelease
    return [b autorelease];
}


-(void)setName:(NSString *)name{
    if(_name!=name);
    [_name release];
    _name=[name retain];
}


@end

执行

//Boy类使用Copy的方法
 Boy *boy=[Boy boyWithName:@"张阳阳" hobby:@"玩"];
 Boy *newBoy=[boy copy];
 NSLog(@"%@",newBoy.name);
 //假设自己的类想要实现copy功能,就必须先签订NSCopying协议,然后实现相应的协议方法,initWithZone,之后就能够使用copy的功能
 NSLog(@"%ld",boy.retainCount);
 NSLog(@"%ld",newBoy.retainCount);

结果

2015-07-27 19:13:02.102 OC08,09_内存管理[1644:168242] 张阳阳
2015-07-27 19:14:15.390 OC08,09_内存管理[1653:168927] 1
2015-07-27 19:14:15.390 OC08,09_内存管理[1653:168927] 1

    Boy *boy1=[[Boy alloc] init];
    [boy1 retain];
    [boy1 retain];
    NSLog(@"%ld",boy1.retainCount);
    NSMutableArray *arr=[NSMutableArray arrayWithObjects:boy1, nil];
    NSLog(@"%ld",[arr[0] retainCount]);

结果

2015-07-27 19:14:52.821 OC08,09_内存管理[1660:169279] 3
2015-07-27 19:14:52.822 OC08,09_内存管理[1660:169279] 4

凝视

// 当对象放入到容器Array或者字典中,对面会被容器进行一次持有,就是retain一次,他的引用计数会+1,主要是为了防止空指针的问题
// //等对象从容器移除掉之后,相应的会-1

    Boy *b=[[Boy alloc] init];
    Girl *girl=[[Girl alloc]init];
    b.girls=girl;
    NSLog(@"%ld",girl.retainCount);

    Girl *girl2=[[Girl alloc] init];
    b.girls=girl2;
    NSLog(@"%ld",girl.retainCount);

结果

2015-07-27 19:16:00.235 OC08,09_内存管理[1667:169909] 2
2015-07-27 19:16:00.236 OC08,09_内存管理[1667:169909] 1

一个完整的类写法

//
//  Person.h
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property(nonatomic,retain)NSMutableArray *arr;
@property(nonatomic,copy)NSString *name;
@property(nonatomic,assign)NSInteger age;


-(id)initWithName:(NSString *)name
              age:(NSInteger)age;

+(Person *)personWithName:(NSString *)name
                      age:(NSInteger)age;


@end

//
//  Person.m
//  OC08,09_内存管理
//
//  Created by dllo on 15/7/27.
//  Copyright (c) 2015年 zhozhicheng. All rights reserved.
//

#import "Person.h"

@implementation Person

-(id)initWithName:(NSString *)name
              age:(NSInteger)age{
    self=[super init];
    if (self) {
        self.name=name;
        self.age=age;
        //对象创建之后,里面的数组也会创建好,不用在外面进行创建,避免由于忘了,造成问题
        self.arr=[NSMutableArray array];
    }return self;
}

+(Person *)personWithName:(NSString *)name
                      age:(NSInteger)age{
    Person *per=[[Person alloc] initWithName:name age:age];
    return [per autorelease];

}
-(void)dealloc{
    [_arr release];
    [_name release];
    //age是栈区的,我们操作的是堆区
}


@end

    Person *per=[[Person alloc] initWithName:@"张阳阳" age:20];
    [per.arr addObject:@"1" ];
    NSLog(@"%@",per.arr);

结果

2015-07-27 19:18:09.427 OC08,09_内存管理[1675:171354] (
    1
)