[Objective-C]OC中的Dealloc方法详解

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;@end
2: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