对模型对象进行归档

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

@interface FourLines : NSObject <NSCoding,NSCopying>{
NSString *field1;
NSString *field2;
NSString *field3;
NSString *field4;
}

@property (nonatomic,retain)NSString *field1;
@property (nonatomic,retain)NSString *field2;
@property (nonatomic,retain)NSString *field3;
@property (nonatomic,retain)NSString *field4;

@end

#import "FourLines.h"

#define kField1Key    @"Field1"
#define kField2Key    @"Field2"
#define kField3Key    @"Field3"
#define kField4Key    @"Field4"

@implementation FourLines

@synthesize field1;
@synthesize field2;
@synthesize field3;
@synthesize field4;

/**
将对象编码到文档中
*/
#pragma mark NSCoding
-(void)  encodeWithCoder:(NSCoder *)enCoder{

[enCoder encodeObject:field1 forKey:kField1Key];
[enCoder encodeObject:field2 forKey:kField2Key];
[enCoder encodeObject:field3 forKey:kField3Key];
[enCoder encodeObject:field4 forKey:kField4Key];
}

/**
通过对文档进行解码来常见一个新对象。
*/
-(id)initWithCoder:(NSCoder *)decoder{
if (self = [super init]) {
field1 = [[decoder decodeObjectForKey:kField1Key] retain];
field2 = [[decoder decodeObjectForKey:kField2Key] retain];
field3 = [[decoder decodeObjectForKey:kField3Key] retain];
field4 = [[decoder decodeObjectForKey:kField4Key] retain];
}
return self;
}

#pragma mark -
#pragma mark NSCopying
-(void)copyWithZone:(NSZone *)zone{
FourLines *copy = [[[self class] allocWithZone:zone] init ];
copy.field1 = [[self.field1 copyWithZone:zone] autorelease];
copy.field2 = [[self.field2 copyWithZone:zone] autorelease];
copy.field3 = [[self.field3 copyWithZone:zone] autorelease];
copy.field4 = [[self.field4 copyWithZone:zone] autorelease];

return copy;
}
@end

#import <UIKit/UIKit.h>

#define kFileName    @"data.list"
#define kFileName    @"archive"
#define kDataKey    @"Data"

@interface PersistenceViewController : UIViewController {
UITextField *field1;
UITextField *field2;
UITextField *field3;
UITextField *field4;
}
@property (nonatomic,retain)IBOutlet UITextField *field1;
@property (nonatomic,retain)IBOutlet UITextField *field2;
@property (nonatomic,retain)IBOutlet UITextField *field3;
@property (nonatomic,retain)IBOutlet UITextField *field4;

- (NSString *)dataFilePath;
-(void)applicationWillResignActive:(NSNotification *)notification;

@end

#import "PersistenceViewController.h"
#import "FourLines.h"

@implementation PersistenceViewController
@synthesize field1;
@synthesize field2;
@synthesize field3;
@synthesize field4;

//用于返回数据文件的完整路径名，它通过查找Document目录并对对其附加kFilename累执行该操作。
-(NSString *)dataFilePath{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
return [documentsDirectory stringByAppendingFormat:kFileName];
}

#pragma mark -

/*
// The designated initializer. Override to perform setup that is required before the view is loaded.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
*/

/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
//在该方法中，我们做了一下操作
/**
1,检查数据文件是否存在
2，数据文件存在，使用该引用订阅UIApplicationWillReSignActiveNotification.
3,我们使用NSNotificationCenter的默认实例，以及addObserver：select：name：object方法。我们传递一个observer即self、这就意味着
PersistenceViewController是需要通知的对象。
*/
- (void)viewDidLoad {
NSString *filePath = [self dataFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
field1.text = [array objectAtIndex:0];
field2.text = [array objectAtIndex:1];
field3.text = [array objectAtIndex:2];
field4.text = [array objectAtIndex:3];

[array release];

NSData *data = [[NSMutableData alloc] initWithContentsOfFile:[self dataFilePath]];

NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];

FourLines *fourLine = [unarchiver decodeObjectForKey:kDataKey];

[unarchiver finishDecoding];

field1.text = fourLine.field1;
field2.text = fourLine.field2;
field3.text = fourLine.field3;
field4.text = fourLine.field4;

[unarchiver release];
[data release];

}

UIApplication *app = [UIApplication sharedApplication];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(applicationWillResignActive:)
name:UIApplicationWillResignActiveNotification
object:app];
[super viewDidLoad];
}

/**

*/
-(void)applicationWillResignActive:(NSNotification *)notification{
NSMutableArray *array = [[NSMutableArray alloc] init ];
[array addObject:field1.text];
[array addObject:field2.text];
[array addObject:field3.text];
[array addObject:field4.text];

[array writeToFile: [self dataFilePath] atomically:YES];
[array release];

FourLines *fourLine = [[FourLines alloc] init];
fourLine.field1 = field1.text;
fourLine.field2 = field2.text;
fourLine.field3 = field3.text;
fourLine.field4 = field4.text;

NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:fourLine
forKey:kDataKey];
[archiver finishEncoding];
[data writeToFile:[self dataFilePath] atomically:YES];
[fourLine release];
[archiver release];
[data release];

}

/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/

- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];

// Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
self.field1 = nil;
self.field2 = nil;
self.field3 = nil;
self.field4 = nil;
[super viewDidUnload];
}

- (void)dealloc {
[field1 release];
[field2 release];
[field3 release];
[field4 release];
[super dealloc];
}

@end