关于数据的归档存入文件和读取文件

需求：我们都知道NSArry中如果存放的是普通的字符串类型，是很容易存入到plist文件中，也很容易从文件中读取出来，那如果NSArray中存放的是自定义的Person对象呢？该如何存入文件中去呢？

下面我来简单写一个NSArray中继承了NSCoding协议的自定义Person对象，将这个array数组存入到plist文件中，并且能够实现读取文件中的数据的Demo

实现步骤：

1.创建一个SingleView的项目命名为test，然后创建一个自定义的Person对象，具有NSString *name和int age两个属性。

Person.h:

#import <Foundation/Foundation.h>
@interface Person : NSObject<NSCopying,NSCoding>
@property(copy,nonatomic)NSString *name;
@property(assign,nonatomic) int age;
@end

Person.m:

#import "Person.h"

@implementation Person

-(id)copyWithZone:(NSZone *)zone
{
    Person  *p = [[Person alloc] init];  //拷贝函数不需要release,这里用autorelease会报错
    p.name = [self.name copy];
    p.age = self.age;
    return p;
}

//实现NSCoding协议
-(void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:self.name forKey:@"name"];
    [aCoder encodeInt:self.age forKey:@"age"]; //这儿要根据不同的类型来写encode的类型
}
//反序列化提取成员变量
-(id)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super init]) {
        if (aDecoder == nil) {
            return self;
        }
        self.name = [aDecoder decodeObjectForKey:@"name"];
        self.age = [aDecoder decodeIntForKey:@"age"]; //这儿也是，如果是int类型就写decodeIntForKey
    }
    return self;
}

-(NSString *)description
{
    return [NSString stringWithFormat:@"%@,%d",self.name,self.age];
}

@end

2.创建一个ViewController来实现数据的的保存

ViewController.h:

#import <UIKit/UIKit.h>
#import "Person.h"  
@interface DXWViewController : UIViewController
@property(nonatomic,retain)NSArray *Array;
@property(nonatomic,retain)Person *per;
@end

ViewController.m:

#import "DXWViewController.h"
#define kSaveKeyMarkerLines (@"person")
@interface DXWViewController ()

@end

@implementation DXWViewController

-(NSString *)getPath
{
    //用来获得Document地址
	NSArray *arr = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);//注意：这里是NSDocument不是NSDocumentation,特别注意
    NSLog(@"%@",arr);
    //在地址上增加文件
    NSString *path = [arr[0] stringByAppendingPathComponent:@"Person.plist"];
    NSLog(@"%@",path);
    return path;
}

//传入可变数组和地址
//序列化数据
- (BOOL)saveMarkers:(NSMutableArray *)markers toFilePath:(NSString *)filePath
{
    BOOL f;
    NSMutableData *data = [[NSMutableData alloc] init];
    NSKeyedArchiver *vdArchiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    [vdArchiver encodeObject:markers forKey:kSaveKeyMarkerLines];
    [vdArchiver finishEncoding];
    f = [data writeToFile:filePath atomically:YES];
    [vdArchiver release];
    [data release];
    return f;
}
//传入地址，返回可变数组
//反序列化数据
- (NSMutableArray *)loadMarkersFromFilePath:(NSString *)filePath {
    NSMutableArray *markers = nil;
    if (filePath == nil || [filePath length] == 0 ||
        [[NSFileManager defaultManager] fileExistsAtPath:filePath] == NO) {
        markers = [[[NSMutableArray alloc] init] autorelease];
    } else {
        NSData *data = [[NSData alloc] initWithContentsOfFile:filePath];
        NSKeyedUnarchiver *vdUnarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        markers = [vdUnarchiver decodeObjectForKey:kSaveKeyMarkerLines];
        NSLog(@"++++%@",markers);
        [vdUnarchiver finishDecoding];
        [vdUnarchiver release];
        [data release];
    }
    return markers;
}


- (void)viewDidLoad
{
    [super viewDidLoad];
	Person *p1 = [[Person alloc] init];
    p1.name = @"dingxiaowei";
    p1.age = 22;
    Person *p2 = [[Person alloc] init];
    p2.name = @"wangning";
    p2.age = 33;
    self.Array  = [NSArray arrayWithObjects:p1,p2, nil];
    //保存到文件
    [self saveMarkers:self.Array toFilePath:[self getPath]];
    //从文件中获取数据
    NSMutableArray *arr = [self loadMarkersFromFilePath:[self getPath]];
    NSLog(@"归档后提取的数据:\n%@",arr);
}


@end

如何寻找创建在沙盒中的文件？

点击一下mac机上的前往功能菜单->然后按下Alt键，会跳出一个资源库的一个隐藏文件->Application Support->iPhone Simulator->6.1(看你当前运行的模拟器的版本)->Applications->对应的文件->Documents->xxx.plist

运行结果：

2013-08-26 14:04:47.101 test[1442:c07]归档后提取的数据:
(
    "dingxiaowei,22",
    "wangning,33"
)