IOS基础 Day-1手动内存管理

辞职回家打算自学IOS开发，就在借个地方记录一下

Day-1      手动内存管理                  

一旦内存占用超过40m 45m时分别发生警告，一旦超过120m 系统将kill你的app 发生闪退

主要要防止发生的问题:

1.野指针操作

2.内存泄漏

理解retain和assign的区别和 retain的原理

Main

  1  //
  2 //  main.m
  3 //  1-1内存管理
  4 //
  5 //  Created by k on 14-8-24.
  6 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
  7 //
  8
  9 #import <Foundation/Foundation.h>
 10 #import "Person.h"
 11 #import "Car.h"
 12 void withParam(Person *p)
 13 {
 14     [p retain];
 15     NSLog(@"withParam : %@ ,retainCount : %lu",p.myName,(unsigned long)[p retainCount]);
 16     [p release];
 17 }
 18
 19 void test1()
 20 {
 21     Person * p1=[[Person alloc ]init];
 22
 23     NSLog(@"retainCount = %lu", (unsigned long)[p1 retainCount]);
 24
 25
 26     p1.myName=@"haha";
 27
 28     NSLog(@"p1 : %@",p1);
 29
 30     Person * p2 = [p1 retain];
 31
 32     NSLog(@"retainCount = %lu", (unsigned long)[p1 retainCount]);
 33
 34
 35     p2.myName=@"gaga";
 36
 37     NSLog(@"p1 : %@",p1);
 38
 39     NSLog(@"p2 : %@",p2);
 40
 41     withParam(p2);
 42
 43
 44     [p2 release];
 45
 46     [p1 release];
 47
 48     p1=nil;
 49
 50     NSLog(@"%@",p1);//如果p1！＝nil 则会发生内存泄露
 51
 52     NSLog(@"%lu", [p1 retainCount]);//nil 但是不报错
 53 }
 54
 55 void test2()
 56 {
 57     Car * c1=[[Car alloc ] init:@"haha"];//初始化 带参数 的对象
 58
 59     NSLog(@"%@",c1);
 60
 61     [c1 release];
 62 }
 63
 64 void test3(){
 65     Person * p1=[[Person alloc]init:@"ak"];
 66
 67     Car * c1= [[Car alloc]init:@"雪弗兰"];
 68
 69     [p1 setCar:c1];
 70
 71     [p1 run];
 72
 73     //1
 74     // NSLog(@"p1 retainCount : %lu", [p1 retainCount]);
 75     //1
 76     //NSLog(@"c1 retainCount : %lu", [c1 retainCount]);
 77
 78       [c1 release];
 79
 80     [p1 release];
 81 }
 82
 83 void test4()
 84 {
 85     //测试property的retain
 86     Person * p1=[[Person alloc]init];
 87
 88     Car * c1=[[Car alloc]init];
 89
 90     Car * c2= [[Car alloc]init];
 91
 92     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
 93
 94
 95     p1.car=c1;
 96
 97
 98     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
 99
100
101     p1.car=c2;
102
103     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
104
105     NSLog(@"c2:%lu",(unsigned long)[c2 retainCount]);
106
107     [c1 release];
108     [c2 release];
109     [p1 release];
110 }
111
112 void test5()
113 {
114     Person * p1=[[Person alloc]init];
115
116     Car * c1=[[Car alloc]init];
117
118     Car * c2= [[Car alloc]init];
119
120     //1
121     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
122     //1
123     NSLog(@"c2:%lu",(unsigned long)[c2 retainCount]);
124
125
126
127     [p1 setCar2:c1];
128
129     //2
130     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
131
132
133     [p1 setCar2:c2];
134
135     //1
136     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
137
138     //2
139     NSLog(@"c2:%lu",(unsigned long)[c2 retainCount]);
140
141
142
143     NSString * s1=@"aaa";
144
145    // NSString * [email protected]"bbb";
146
147     NSLog(@"s1:%lu",(unsigned long)[s1 retainCount]);
148
149     [p1 setMyName:s1];
150
151     NSLog(@"s1:%lu",(unsigned long)[s1 retainCount]);
152
153     [c1 release];
154     [c2 release];
155     [p1 release];
156
157 }
158 int main(int argc, const char * argv[])
159 {
160
161     @autoreleasepool {
162
163        // test1();
164        // test2();
165        // test3();
166         test4();
167         //test5();
168     }
169     return 0;
170 }

Person.h

 1 //
 2 //  Person.h
 3 //  1 基础知识
 4 //
 5 //  Created by k on 14-8-24.
 6 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 7 //
 8
 9 #import <Foundation/Foundation.h>
10 #import "Car.h"
11
12 @interface Person : NSObject
13 @property (nonatomic,assign , readwrite ) NSString * myName  ;
14 @property (nonatomic,retain,readwrite) Car * car;
15 -(instancetype)init:(NSString *) Name;
16 -(void) speakMyName;
17 -(void)setCar:(Car *) car;
18 -(void) run;
19
20
21
22 -(void)setCar2:(Car*)car2;
23 @end
24   

person.m

 1 //
 2 //  Person.m
 3 //  1 基础知识
 4 //
 5 //  Created by k on 14-8-24.
 6 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 7 //
 8
 9 #import "Person.h"
10
11 @implementation Person
12 {
13     Car * _car2;
14 }
15
16 - (instancetype)init:(NSString *) Name
17 {
18     self = [super init];
19     if (self) {
20         _myName=Name;
21     }
22     return self;
23 }
24
25 -(void)speakMyName{
26
27     NSLog(@"大家好我的名字叫%@",_myName);
28
29 }
30
31
32
33 -(void)setCar2:(Car*)car2
34 {
35   if(_car2!=car2)
36   {
37       [_car2 release];
38       _car2=car2;
39       [car2 retain ];
40   }
41 }
42
43 -(void)run{
44
45     NSLog(@"%@ 驾驶着 %@",_myName,_car.carName);
46
47 }
48
49 - (NSString *)description
50 {
51     return [NSString stringWithFormat:@"this is Person,myName=%@", _myName];
52 }
53
54 - (void)dealloc
55 {
56     [_car2 release];
57     [super dealloc];
58     NSLog(@"Person对象被销毁");
59 }
60 @end

Car.h

 1 //
 2 //  Car.h
 3 //  1 基础知识
 4 //
 5 //  Created by k on 14-8-24.
 6 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 7 //
 8
 9 #import <Foundation/Foundation.h>
10
11 @interface Car : NSObject
12
13 @property (nonatomic,assign,readwrite) NSString * carName;
14 - (instancetype)init:(NSString *)Name;
15
16 -(void)run;
17 @end

Car.m

 1 //
 2 //  Car.m
 3 //  1 基础知识
 4 //
 5 //  Created by k on 14-8-24.
 6 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 7 //
 8
 9 #import "Car.h"
10
11 @implementation Car
12
13 - (instancetype)init:(NSString *)Name
14 {
15     self = [super init];
16     if (self) {
17         _carName=Name;
18     }
19     return self;
20 }
21 -(void)run
22 {
23
24     NSLog(@"%@ is Running",_carName);
25 }
26 - (NSString *)description
27 {
28     return [NSString stringWithFormat:@"carName : %@", _carName];
29 }
30 - (void)dealloc
31 {
32     [super dealloc];
33     NSLog(@"Car %@ 被销毁",_carName);
34 }
35 @end