object-c的Dealloc

柔光的暖阳◎ 2023-10-18 22:29 31阅读 0赞

当你自己的类中包含有其它对象时，就得负责dealloc它们，通过重写dealloc函数。  
  
**1. 例子代码：**  
//1. AddressCard.h  
\#import <Foundation/NSObject.h>  
\#import <Foundation/NSString.h>  
  
  
@interface AddressCard: NSObject \{  
NSString \*first;  
NSString \*last;  
NSString \*email;  
\}  
  
\-(AddressCard\*) initWithFirst: (NSString\*) f last: (NSString\*) l email: (NSString\*) e;  
\-(NSString\*) first;  
\-(NSString\*) last;  
\-(NSString\*) email;  
\-(void) setFirst: (NSString\*) f;  
\-(void) setLast: (NSString\*) l;  
\-(void) setEmail: (NSString\*) e;  
\-(void) setFirst: (NSString\*) f last: (NSString\*) l email: (NSString\*) e;  
\-(void) setFirst: (NSString\*) f last: (NSString\*) l;  
\-(void) print;  
@end  
  
  
//2. AddressCard.m  
\#import "AddressCard.h"  
\#import <stdio.h>  
  
  
@implementation AddressCard  
\-(AddressCard\*) initWithFirst: (NSString\*) f last: (NSString\*) l email: (NSString\*) e \{  
self = \[super init\];  
  
  
if ( self ) \{  
\[self setFirst: f last: l email: e\];  
\}  
  
  
return self;  
\}  
  
  
\-(NSString\*) first \{  
return first;  
\}  
  
  
\-(NSString\*) last \{  
return last;  
\}  
  
  
\-(NSString\*) email \{  
return email;  
\}  
  
  
\-(void) setFirst: (NSString\*) f \{  
\[f retain\];  
\[first release\];  
first = f;  
\}  
  
  
\-(void) setLast: (NSString\*) l \{  
\[l retain\];  
\[last release\];  
last = l;  
\}  
  
  
\-(void) setEmail: (NSString\*) e \{  
\[e retain\];  
\[email release\];  
email = e;  
\}  
  
  
\-(void) setFirst: (NSString\*) f last: (NSString\*) l email: (NSString\*) e \{  
\[self setFirst: f\];  
\[self setLast: l\];  
\[self setEmail: e\];  
\}  
  
  
\-(void) setFirst: (NSString\*) f last: (NSString\*) l \{  
\[self setFirst: f\];  
\[self setLast: l\];  
\}  
  
  
\-(void) print \{  
printf( "%s %s <%s>", \[first cString\], \[last cString\], \[email cString\] );  
\}  
  
  
\-(void) dealloc \{  
\[first release\];  
\[last release\];  
\[email release\];  
  
  
\[super dealloc\];  
\}  
@end  
  
  
//3. main.m  
\#import "AddressCard.h"  
\#import <Foundation/NSString.h>  
\#import <stdio.h>  
  
  
int main( int argc, const char \*argv\[\] ) \{  
NSString \*first =\[\[NSString alloc\] initWithCString: "Tom"\];  
NSString \*last = \[\[NSString alloc\] initWithCString: "Jones"\];  
NSString \*email = \[\[NSString alloc\] initWithCString: "tom@jones.com"\];  
AddressCard \*tom = \[\[AddressCard alloc\] initWithFirst: first last: last email: email\];  
  
  
// we'return done with the strings, so we must dealloc them  
\[first release\];  
\[last release\];  
\[email release\];  
  
  
// print to show the retain count  
printf( "Retain count: %i\\n", \[\[tom first\] retainCount\] );  
\[tom print\];  
printf( "\\n" );  
  
// free memory  
\[tom release\];  
  
  
return 0;  
\}  
  
  
**2. 编译运行：**  
gcc -fconstant-string-class=NSConstantString -c main.m -I /GNUstep/System/Library/Headers  
gcc -c AddressCard.m -I /GNUstep/System/Library/Headers  
gcc main.o AddressCard.o -o main -L /GNUstep/System/Library/Libraries/ -lobjc -lgnustep-base  
  
  
$ ./main.exe  
Retain count: 1  
Tom Jones <tom@jones.com>  
  
**3. 说明：**  
 （1）. 一定要先用retain保留一份引用计数，用完它之后，才能再调用release去使得引用计数减1；

（2）. 这个实例展示了定义自己的类时，如果成员变量是其它对象的引用时，该如何处理。

**4. 补充：**

关于更多的内存使用，回收的内容，可以参考下面给出的链网址来进一步学习和理解：

[http://vinceyuan.cnblogs.com/][http_vinceyuan.cnblogs.com]

[http_vinceyuan.cnblogs.com]: http://vinceyuan.cnblogs.com/