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）