第十九讲：Objective-C内存管理之“MyArray”
该主题主要内容通过自创一个数组“MyArray”来说明内存管理中的retainCount问题：1、创建一个数组_objs（C语言方法）；
2、数组中包含三个基本方法 addObject、removeObject、removeAll，通过在对象中添加对象与删除对象来理解内存管理的黄金法则；
3、创建一个类Dog，做为数组操作的基本元素；
4、创建一个数组对象array；
5、通过使用addObject将对象元素dog添加到数组中，dog对象本身完成初始化后会release，但在数据中的元素因为需要使用该对象，所以要保证dog对象本身release时所以权由数组控制；
6、数组自身被释放（release）后，及时将数组中的对象元素进行释放操作；
代码实现如下：
Dog.h
//
//Dog.h
//Memory_myArray1
//
//Created by yusian on 14-1-12.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface Dog : NSObject
{
int _ID;
}
@property int ID;
@end
Dog.m
//
//Dog.m
//Memory_myArray1
//
//Created by yusian on 14-1-12.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import "Dog.h"
@implementation Dog
@synthesize ID = _ID;
- (void) dealloc{
NSLog(@"dog %d is dealloc",_ID);
;
}
@end
myArray.h
//
//myArray.h
//Memory_myArray1
//
//Created by yusian on 14-1-12.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import <Foundation/Foundation.h>
#import "Dog.h"
@interface myArray : NSObject
{
NSUInteger _count;
id _objs;
}
@property (assign, readonly) NSUInteger count;
- (void) addObject:(id)object;
- (void) removeObjectAtIndex:(NSUInteger)index;
- (void) removeAll;
@end
myArray.m
//
//myArray.m
//Memory_myArray1
//
//Created by yusian on 14-1-12.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import "myArray.h"
@implementation myArray
@synthesize count = _count;
- (id) init{
self = ;
if (self) {
_count = 0;
}
return self;
}
- (void) addObject:(id)object{
if (_count >= 512)
return;
_objs = ;//此步骤是关键！！！（对象在这里进行retain操作，因为对象自身会做release操作，数组中的指针会因此而变成野指针）
_count ++;
}
- (void) removeObjectAtIndex:(NSUInteger)index{
id obj = _objs;
;
_objs = nil;
}
- (void) removeAll{
for (int i = 0; i < _count; i ++){
;
}
}
- (void) dealloc{
NSLog(@"myArray is dealloc");
;
;
}
@end
main.m
//
//main.m
//Memory_myArray1
//
//Created by yusian on 14-1-12.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import <Foundation/Foundation.h>
#import "myArray.h"
#import "Dog.h"
int main(int argc, const char * argv[])
{
@autoreleasepool {
myArray * array = [ init];
for (int i = 0; i < 3; i ++){
Dog * dog = [ init];
;
;
;
NSLog(@"dog %d retainCount is %ld",,);
}
//NSLog(@"%ld",);
;
}
return 0;
}
运行结果：
2014-01-12 16:31:55.660 Memory_myArray1 dog 0 retainCount is 1
2014-01-12 16:31:55.662 Memory_myArray1 dog 1 retainCount is 1
2014-01-12 16:31:55.662 Memory_myArray1 dog 2 retainCount is 1
2014-01-12 16:31:55.662 Memory_myArray1 myArray is dealloc
2014-01-12 16:31:55.663 Memory_myArray1 dog 0 is dealloc
2014-01-12 16:31:55.663 Memory_myArray1 dog 1 is dealloc
2014-01-12 16:31:55.663 Memory_myArray1 dog 2 is dealloc
Program ended with exit code: 0
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