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                  

---

 

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];
    
    //1
    NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
    //1
    NSLog(@"c2:%lu",(unsigned long)[c2 retainCount]);
    

    
    [p1 setCar2:c1];
    
    //2
    NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
    
    
    [p1 setCar2:c2];
    
    //1
    NSLog(@"c1:%lu",(unsigned long)[c1 retainCount]);
    
    //2
    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 0;
}

 

 

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