[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]; }

     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，然後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  @interface Vehicle : NSObject { @private NSString *_name; } -(id)initWithName:(NSString *)name; @end

#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  #import "Vehicle.h" @class Engine; @interface Car : Vehicle { Engine *_engine; } -(void)setEngine:(Engine *)engine; @end 

#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 

#import  #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; }