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                  

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主要内容:release  retain必须配对好，不然会占用内存 慢慢积累导致错误

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

  //
 //  main.m
 //  1-1内存管理
 //
 //  Created by k on 14-8-24.
 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 //

 #import <Foundation/Foundation.h>
 #import "Person.h"
 #import "Car.h"
 void withParam(Person *p)
 {
     [p retain];
     NSLog(@"withParam : %@ ,retainCount : %lu",p.myName,(unsigned long)[p retainCount]);
     [p release];
 }

 void test1()
 {
     Person * p1=[[Person alloc ]init];

     NSLog(@"retainCount = %lu", (unsigned long)[p1 retainCount]);

     p1.myName=@"haha";

     NSLog(@"p1 : %@",p1);

     Person * p2 = [p1 retain];

     NSLog(@"retainCount = %lu", (unsigned long)[p1 retainCount]);

     p2.myName=@"gaga";

     NSLog(@"p1 : %@",p1);

     NSLog(@"p2 : %@",p2);

     withParam(p2);

     [p2 release];

     [p1 release];

     p1=nil;

     NSLog(@"%@",p1);//如果p1！＝nil 则会发生内存泄露

     NSLog(@"%lu", [p1 retainCount]);//nil 但是不报错
 }

 void test2()
 {
     Car * c1=[[Car alloc ] init:@"haha"];//初始化 带参数 的对象

     NSLog(@"%@",c1);

     [c1 release];
 }

 void test3(){
     Person * p1=[[Person alloc]init:@"ak"];

     Car * c1= [[Car alloc]init:@"雪弗兰"];

     [p1 setCar:c1];

     [p1 run];

     //1
     // NSLog(@"p1 retainCount : %lu", [p1 retainCount]);
     //1
     //NSLog(@"c1 retainCount : %lu", [c1 retainCount]);

       [c1 release];

     [p1 release];
 }

 void test4()
 {
     //测试property的retain
     Person * p1=[[Person alloc]init];

     Car * c1=[[Car alloc]init];

     Car * c2= [[Car alloc]init];

     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);

     p1.car=c1;

     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);

     p1.car=c2;

     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);

     NSLog(@"c2:%lu",(unsigned long)[c2 retainCount]);

     [c1 release];
     [c2 release];
     [p1 release];
 }

 void test5()
 {
     Person * p1=[[Person alloc]init];

     Car * c1=[[Car alloc]init];

     Car * c2= [[Car alloc]init];

     //
     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
     //
     NSLog(@"c2:%lu",(unsigned long)[c2 retainCount]);

     [p1 setCar2:c1];

     //
     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);

     [p1 setCar2:c2];

     //
     NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);

     //
     NSLog(@"c2:%lu",(unsigned long)[c2 retainCount]);

     NSString * s1=@"aaa";

    // NSString * s2=@"bbb";

     NSLog(@"s1:%lu",(unsigned long)[s1 retainCount]);

     [p1 setMyName:s1];

     NSLog(@"s1:%lu",(unsigned long)[s1 retainCount]);

     [c1 release];
     [c2 release];
     [p1 release];

 }
 int main(int argc, const char * argv[])
 {

     @autoreleasepool {

        // test1();
        // test2();
        // test3();
         test4();
         //test5();
     }
     return ;
 }

 

Person.h

 //
 //  Person.h
 //  1 基础知识
 //
 //  Created by k on 14-8-24.
 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 //

 #import <Foundation/Foundation.h>
 #import "Car.h"

 @interface Person : NSObject
 @property (nonatomic,assign , readwrite ) NSString * myName  ;
 @property (nonatomic,retain,readwrite) Car * car;
 -(instancetype)init:(NSString *) Name;
 -(void) speakMyName;
 -(void)setCar:(Car *) car;
 -(void) run;

 -(void)setCar2:(Car*)car2;
 @end
   

person.m

 //
 //  Person.m
 //  1 基础知识
 //
 //  Created by k on 14-8-24.
 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 //

 #import "Person.h"

 @implementation Person
 {
     Car * _car2;
 }

 - (instancetype)init:(NSString *) Name
 {
     self = [super init];
     if (self) {
         _myName=Name;
     }
     return self;
 }

 -(void)speakMyName{

     NSLog(@"大家好我的名字叫%@",_myName);

 }

 -(void)setCar2:(Car*)car2
 {
   if(_car2!=car2)
   {
       [_car2 release];
       _car2=car2;
       [car2 retain ];
   }
 }

 -(void)run{

     NSLog(@"%@ 驾驶着 %@",_myName,_car.carName);

 }

 - (NSString *)description
 {
     return [NSString stringWithFormat:@"this is Person,myName=%@", _myName];
 }

 - (void)dealloc
 {
     [_car2 release];
     [super dealloc];
     NSLog(@"Person对象被销毁");
 }
 @end

Car.h

 //
 //  Car.h
 //  1 基础知识
 //
 //  Created by k on 14-8-24.
 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 //

 #import <Foundation/Foundation.h>

 @interface Car : NSObject

 @property (nonatomic,assign,readwrite) NSString * carName;
 - (instancetype)init:(NSString *)Name;

 -(void)run;
 @end

Car.m

 //
 //  Car.m
 //  1 基础知识
 //
 //  Created by k on 14-8-24.
 //  Copyright (c) 2014年 com.akleee.www. All rights reserved.
 //

 #import "Car.h"

 @implementation Car

 - (instancetype)init:(NSString *)Name
 {
     self = [super init];
     if (self) {
         _carName=Name;
     }
     return self;
 }
 -(void)run
 {

     NSLog(@"%@ is Running",_carName);
 }
 - (NSString *)description
 {
     return [NSString stringWithFormat:@"carName : %@", _carName];
 }
 - (void)dealloc
 {
     [super dealloc];
     NSLog(@"Car %@ 被销毁",_carName);
 }
 @end