Iphone 尝试在Xcode中存档自定义对象时出错

我正试图使用

NSCoder

将一个自定义对象（我的对象是一个图书馆，就像在借书的地方一样）归档到iPhone的文件系统中。但是，当我尝试调用

NSKeyedArchiver archiveRootObject

时，我收到一个错误“无法识别的选择器发送到实例”。库声明

NSCoding

协议并实现所需的方法。我不知所措

对象接口（library.h）：

最后是viewController（libTableViewController.m）

以下是错误：

2011-12-18 12:13:38.799 LibraryFiend2[12877:207] try to archive library to path: /Users/kclary/Library/Application Support/iPhone Simulator/4.3/Applications/71B11434-3307-449A-9E95-5E22034E7FA0/Documents/lib.data
2011-12-18 12:13:38.800 LibraryFiend2[12877:207] -[NSKeyedArchiver encodeObject:forkey:]: unrecognized selector sent to instance 0x4b1a130
2011-12-18 12:13:38.801 LibraryFiend2[12877:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSKeyedArchiver encodeObject:forkey:]: unrecognized selector sent to instance 0x4b1a130'
terminate called after throwing an instance of 'NSException'  

---

如果我用一个简单数组替换我的库对象，它就会工作

您得到异常，因为这一行

[encoder-encodeObject:numCopies-forkey:@“numCopies”]

numCopies
不是对象，它是原语，应该使用
encodeInt:forKey:
方法存储
 不幸的是，这并没有解决问题。我将行更改为：[编码器encodeInt:numCopies-forkey:@“numCopies”]；但我在那行代码中得到了同样的异常。
#import "library.h"

@implementation Library

@synthesize numCopies;
@synthesize location;
@synthesize locationInfo;
@synthesize material;
@synthesize library;

+ (id)library
{
return [[Library alloc] init];  
}

-(void)encodeWithCoder:(NSCoder *)encoder
{
    //for each instance variable, archive it under its variable name
    [encoder encodeObject:numCopies forkey:@"numCopies"];
    [encoder encodeObject:location forkey:@"location"];
    [encoder encodeObject:locationInfo forkey:@"locationInfo"];
    [encoder encodeObject:material forkey:@"material"];
    [encoder encodeObject:library forkey:@"library"];
}

//try to archive the library object
NSString *savePath = pathInDocumentDirectory(@"lib.data");
NSLog(@"try to archive library to path: %@", savePath);
[NSKeyedArchiver archiveRootObject:this_lib toFile:savePath];

2011-12-18 12:13:38.799 LibraryFiend2[12877:207] try to archive library to path: /Users/kclary/Library/Application Support/iPhone Simulator/4.3/Applications/71B11434-3307-449A-9E95-5E22034E7FA0/Documents/lib.data
2011-12-18 12:13:38.800 LibraryFiend2[12877:207] -[NSKeyedArchiver encodeObject:forkey:]: unrecognized selector sent to instance 0x4b1a130
2011-12-18 12:13:38.801 LibraryFiend2[12877:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSKeyedArchiver encodeObject:forkey:]: unrecognized selector sent to instance 0x4b1a130'
terminate called after throwing an instance of 'NSException'