今天来学习一下Dealloc方法的使用。

它的作用是,当对象的引用计数为0，系统会自动调用dealloc方法，回收内存。它的一般写法：

1:-(void)dealloc{

[super dealloc]; }

2:-(void)dealloc{

NSLog(@"laptop dead"); [_cpu release]; [super dealloc]; }(一):为什么需要调用父类的dealloc方法？

子类的某些对象实例是继承自父类的。因此，我们需要调用父类的dealloc方法，来释放父类

拥有的这些对象。

(二):调用的顺序

一般说调用的顺序是，当子类的对象释放完时，然后再释放父类的所拥有的实例。这一点与调用初始化方法，

正好相反

下面使用一个例子来演示一下:

1：父类Vehicle.h

#import <Foundation/Foundation.h> @interface Vehicle : NSObject { @private NSString *_name; } -(id)initWithName:(NSString *)name; @end2:父类Vehicle.m

#import "Vehicle.h"

@implementation Vehicle

-(id)initWithName:(NSString *)name{ self=[super init]; if(self){ _name=[name copy]; } return self; } -(void)dealloc{ NSLog(@"vehicle dead"); [_name release]; [super dealloc]; } @end

3:子类Car.h

#import <Foundation/Foundation.h> #import "Vehicle.h" @class Engine; @interface Car : Vehicle { Engine *_engine; } -(void)setEngine:(Engine *)engine; @end 4:子类Car.m

#import "Car.h"

@implementation Car

-(void)setEngine:(Engine *)engine{ if(_engine!=engine){ [_engine release]; _engine=[engine retain]; } } -(Engine *)engint{ return _engine; } -(void)dealloc{ NSLog(@"Car dead"); [_engine release]; [super dealloc]; } @end 5:测试main.m代码

#import <Foundation/Foundation.h> #import "Engine.h" #import "Car.h" int main(int argc, const char * argv[]) { @autoreleasepool { NSString *name=[[NSString alloc]initWithFormat:@"audi"]; Car *car=[[Car alloc]initWithName:name]; [name release]; Engine *v6=[[Engine alloc]init]; [car setEngine:v6]; [v6 release]; //do something [car release]; } return 0; }运行截图