ios开发中归档的使用

来源：互联网发布：看啪啪视频软件编辑：程序博客网时间：2024/05/17 03:10

1、面向对象的程序在运行的时候会创建一个复杂的对象图，经常要以二进制的方法序列化这个对象图，这个过程叫做Archiving.二进制流可以通过网络或写入文件中

例：NSKeyedArchiver
========================================================*/
NSString *str = @”abc”;
NSString *astr = @”efg”;
NSArray *Array = [NSArray arrayWithObjects:str, astr, nil];

//保存数据
NSString *Path =[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) objectAtIndex:0];

NSString *filename = [PathstringByAppendingPathComponent:@"test"];
[NSKeyedArchiverarchiveRootObject:Array toFile:filename];

str = @”a”;
astr = @”";

//加载数据
NSArray *arr =[NSKeyedUnarchiver unarchiveObjectWithFile:filename];
str = [arr objectAtIndex:0];
astr = [arrobjectAtIndex:1];

NSLog(@”str:%@”,str);
NSLog(@”astr:%@”,astr);

2、在nsstring 的类的定义中已经添加了协议即他是实现了nscoding 代理的方法的。

@interface NSString : NSObject

NScoding 是一个协议，主要有下面两个方法

-(id)initWithCoder:(NSCoder*)coder;//从coder中读取数据，保存到相应的变量中，即反序列化数据

-(void)encodeWithCoder:(NSCoder *)coder;//读取实例变量，并把这些数据写到coder中去。序列化数据

NSCoder 是一个抽象类，抽象类不能被实例话，只能提供一些想让子类继承的方法。

NSKeyedUnarchiver 从二进制流读取对象。

NSKeyedArchiver 把对象写到二进制流中去。

一般是在自己定义的类中需要在.h 文件中加入

在.m 文件众实现他的的两个代理方法，这个代理方法将会被自动调用

例如对一个数据类的封装如下：

@interface Restaurant : NSObject {
    NSString*shopID;
    NSString*title;
    NSString*discount;
    NSString*address;
}

@property (nonatomic, copy) NSString *shopID;
@property (nonatomic, copy) NSString *title;
@property (nonatomic, copy) NSString *discount;
@property (nonatomic, copy) NSString *address;
@end

@implementation Restaurant
@synthesize shopID,title,discount,address;
-(void)dealloc
{
    [shopIDrelease];
    [titlerelease];
    [discountrelease];
    [addressrelease];

[superdealloc];
}

- (id)initWithCoder:(NSCoder *)coder
{
    if(self = [super init]) {
        shopID= [[coder decodeObjectForKey:@"shopid"] retain];
        title  =[[coder decodeObjectForKey:@"title"] retain];
        discount=[[coderdecodeObjectForKey:@"discount"] retain];
        address=[[coderdecodeObjectForKey:@"address"] retain]；
    }
    returnself;
}

-(void)encodeWithCoder:(NSCoder *)coder
{
    [coderencodeObject:shopID forKey:@"shopid"];
    [coderencodeObject:title forKey:@"title"];
    [coderencodeObject:discount forKey:@"discount"];
    [coderencodeObject:addressforKey:@"address"];
}
@end

下一步就是保存和加载数据了：

注：history对象是一个NSMutableArray数组，用来装Restaurant对象。

-(void)saveArchiver //保存
{

//获取路径和保存文件

    NSArray  *paths= NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
    NSString*filename = [[paths objectAtIndex:0]stringByAppendingPathComponent:@"history.dat"];

    if(history && [history count]>0) {
        [NSKeyedArchiverarchiveRootObject:history toFile:filename];
    }else{
        //删除归档文件
        NSFileManager *defaultManager= [NSFileManager defaultManager];
        if([defaultManager isDeletableFileAtPath:filename]) {
            [defaultManagerremoveItemAtPath:filename error:nil];
        }
    }
}

-(void)loadArchiver      //加载
{
    NSArray  *paths= NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
    NSString*filename = [[paths objectAtIndex:0]stringByAppendingPathComponent:@"history.dat"];
    self.history=[NSKeyedUnarchiver unarchiveObjectWithFile:filename];
}

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