第五讲：Obj-C 内存管理3 - 自定义MyArray

转：http://tigercat1977.blog.163.com/blog/static/2141561122012111294042162/

第五讲：Obj-C 内存管理3 - 自定义MyArray 

2012-12-12 09:40:42|  分类： Objective-C |  标签：objective-c  |字号大中小 订阅

主要内容
      了解 NSMutableArray 如何实现
      进一步深入内存管理
      进一步深入内存管理！
      进一步深入内存管理！！
      进一步深入内存管理！！！

NSMutableArray 典型用法
      NSMutableArray *array = [[NSMutableArray alloc] init];
      for (int i = 0; i < 10; i++)
      {
            Dog *dog = [[Dog alloc] init];
            [dog setID:i];
            [array addObject:dog];
            [dog release];
      }
      for (Dog *d in array)
      {
            NSLog(@"dog is %d", [d ID]);
      }
      [array release];

MyArray 提供方法
      - (NSInteger) addObject:(id)object;     // 往类里面加个对象                   
      - (id) objectAtIndex:(NSUInteger) index;    // 取得第几项的对象
      - (void) removeObjectAtIndex:(NSUInteger) index;  // 删掉某一项
      - (void) removeAll;   //删掉所有的对象

举例子 （四条狗）

//  Dog.h
#import <Foundation/Foundation.h>

@interface Dog : NSObject
{
    int _ID;
}
@property (assign) int ID;
@end

//  Dog.m
#import "Dog.h"
@implementation Dog
@synthesize  ID = _ID;

// 当对象计数器到 0 的时候 自动会调用
- (void) dealloc
{
    NSLog(@"dog id %d dealloc", _ID);
    [super dealloc];
}
@end 

//  main.m
#import <Foundation/Foundation.h>
#import "Dog.h"

int main (int argc, const char * argv[])
{
    @autoreleasepool
    {
        NSLog(@"Hello, World!");
        NSMutableArray *array = [[NSMutableArray alloc] init];
        for (int i =0; i < 4; i++)
        {
            Dog *d = [[Dog alloc] init];
            [d setID:i];
            NSLog(@"dog%i retainCount1 %ld", i, [d retainCount]);
            [array addObject:d];
            NSLog(@"dog%i retainCount2 %ld", i, [d retainCount]);
            [d release];
        }
        [array release];
    }
    return 0;
}
/* 输出结果：
 Hello, World!
 dog0 retainCount1 1
 dog0 retainCount2 2
 dog1 retainCount1 1
 dog1 retainCount2 2
 dog2 retainCount1 1
 dog2 retainCount2 2
 dog3 retainCount1 1
 dog3 retainCount2 2
 dog id 0 dealloc
 dog id 1 dealloc
 dog id 2 dealloc
 dog id 3 dealloc
*/

×××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××
举例子 （用 MyArray 提供方法）

//  Dog.h
#import <Foundation/Foundation.h>

@interface Dog : NSObject
{
    int _ID;
}
@property (assign) int ID;
@end

//  Dog.m
#import "Dog.h"
@implementation Dog
@synthesize  ID = _ID;

// 当对象计数器到 0 的时候 自动会调用
- (void) dealloc
{
    NSLog(@"dog id %d dealloc", _ID);
    [super dealloc];
}
@end 

//  MyArray.h
#import <Foundation/Foundation.h>
@interface MyArray : NSObject
{
    NSUInteger _count;
    // 数组当前有几项元素
    id _objs[512];
    // 创建了一个 512 项的数组 4＊512 
}
@property (assign, readonly) NSUInteger count;
//  往 MyArray 中加入一项元素
- (void) addObject:(id) object;
// 取得第 index 项元素
- (id) objectAtIndex:(NSUInteger) index;
// 删除第 index 项元素
- (void) removeObjectAtIndex:(NSUInteger) index;
// 删除所有元素
- (void) removeAll;
@end 

//  MyArray.m
#import "MyArray.h"
@implementation MyArray
@synthesize  count = _count;
- (id) init
{
    self = [super init];
    if (self)
    {
        _count = 0;
    }
    return  self;
}
- (void) addObject:(id) object
{
    if (_count >= 512) 
        return;
    _objs[_count] = [object retain];
    _count++;
    // 这里必须要做 [object retain];
}
- (id) objectAtIndex:(NSUInteger)index
{
    return  _objs[index];
}
- (void) removeObjectAtIndex:(NSUInteger)index
{
    id obj = _objs[index];
    [obj release];
    _objs[index] = nil;
}
- (void) removeAll
{
    for (int i =0; i < _count; i++)
    {
        [self removeObjectAtIndex:i];
    }
}
- (void) dealloc
{
    // 在数组对象被 release 到 0 时候调用
    NSLog(@"before remove all");
    [self removeAll];
    NSLog(@"after remove all");
    [super dealloc];
}
@end 

//  main.m
#import <Foundation/Foundation.h>
#import "Dog.h"
#import "MyArray.h"

int main (int argc, const char * argv[])
{
    @autoreleasepool
    {
        NSLog(@"Hello, World!");
        MyArray *myArray = [[MyArray alloc] init];
        for (int i = 0; i < 4; i++)
        {
            Dog *d = [[Dog alloc] init];
            [d setID:i];
            NSLog(@"dog%i retainCount1 is %ld", i, [d retainCount]);
            [myArray addObject:d];
            NSLog(@"dog%i retainCount2 is %ld", i, [d retainCount]);
            [d release];
        }
        [myArray release];        
    }
    return 0;
}
/* 输出结果：
 Hello, World!
 dog0 retainCount1 1
 dog0 retainCount2 2
 dog1 retainCount1 1
 dog1 retainCount2 2
 dog2 retainCount1 1
 dog2 retainCount2 2
 dog3 retainCount1 1
 dog3 retainCount2 2
 dog id 0 dealloc
 dog id 1 dealloc
 dog id 2 dealloc
 dog id 3 dealloc
*/ 

（本讲完）