Objective-C中的@property的retain写法的原理

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目的：解决参数是OC对象的内存泄漏

场景1：在main中参数对象只有一个

=============main.m==================

#import “Person.h”

int main(){

Person *Sam = [Person new];

Car *bmw = [Car new];

[Sam setCar:bmw];

[Sam FuckCar];

[bmw release]; //进行对象回收

//创建了新的一辆车子

Car * landrover= [Car new];

[Sam setCar:landrover];

[Sam FuckCar];

[landrover release]; //进行对象回收

[Sam release] ; }

=======Person.m=============

@implementation

-(void)setCar:(Car *)car{

_car = [_car retain]; }

-(void)FuckCar{

[_car rrun]; }

-(void)dealloc{ // 内存回收后的“遗言”

[_car release];

NSlog(@“Sam is dead!”) ;

[super dealloc]; }

@end

//如果对象参数有2个，在dealloc中只能释放一个对象造成内存泄漏

场景2：对象参数有多个，如果按照场景1就会造成内存泄漏，解决方案

@implementation

-(void)setCar:(Car *)car{

[_car release]; //新增了这一句

_car = [_car retain]; }

-(void)FuckCar{

[_car rrun]; }

-(void)dealloc{ // 内存回收后的“遗言”

[_car release];

NSlog(@“Sam is dead!”) ;

[super dealloc]; }

@end

在新增对象参数之前把旧的对象删除，

场景3：如果对象参数是一个，但是连续传入两次，导致对象的retainCount=0的时候再次retain会造成僵尸对象复活，解决

=============main.m==================

#import “Person.h”

int main(){

Person *Sam = [Person new];

Car *bmw = [Car new];

[Sam setCar:bmw];

[Sam FuckCar];

[bmw release]; //进行对象回收

[Sam setCar:bmw];

[Sam FuckCar];

[Sam release] ; }

================Person.m============

@implementation

-(void)setCar:(Car *)car{

//如果是同一个对象不需要retain和release

if(_car != car){

[_car release];

_car = [_car retain]; } }

-(void)FuckCar{

[_car rrun]; }

-(void)dealloc{ // 内存回收后的“遗言”

[_car release];

NSlog(@“Sam is dead!”) ;

[super dealloc]; }

@end

最终版本的写法就是：@property（nonatomic，retain）Car *car；的语法格式

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