【Objective-C】OC中的Dealloc方法詳解

今天來學習一下Dealloc方法的使用。

它的作用是,當對象的引用計數為0，系統會自動調用dealloc方法，回收內存。它的一般寫法：

1:-(void)dealloc{

    [super dealloc]; }

2:-(void)dealloc{ 
    NSLog(@"laptop dead");     [_cpu release];     [super dealloc]; }
(一):為什么需要調用父類的dealloc方法？

     子類的某些對象實例是繼承自父類的。因此，我們需要調用父類的dealloc方法，來釋放父類

擁有的這些對象。

(二):調用的順序

     一般說調用的順序是，當子類的對象釋放完時，然后再釋放父類的所擁有的實例。這一點與調用初始化方法，

正好相反

下面使用一個例子來演示一下:

1：父類Vehicle.h

#import <Foundation/Foundation.h>  @interface Vehicle : NSObject {     @private     NSString *_name; } -(id)initWithName:(NSString *)name; @end
2:父類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:子類Car.h
#import <Foundation/Foundation.h> #import "Vehicle.h" @class Engine; @interface Car : Vehicle {     Engine *_engine; } -(void)setEngine:(Engine *)engine; @end 
4:子類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:測試main.m代碼
#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; }
運行截圖