【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>@interfaceVehicle:NSObject{@privateNSString*_name;}-(id)initWithName:(NSString*)name;@end
2:父类Vehicle.m
#import "Vehicle.h"
@implementationVehicle
-(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"@classEngine;@interfaceCar:Vehicle{Engine*_engine;}-(void)setEngine:(Engine*)engine;@end
4:子类Car.m
#import "Car.h"
@implementationCar
-(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,constchar* 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];}return0;}
运行截图

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