以代碼實例總結iOS應用開發中數據的存儲方式

2020-07-26 03:27:23

字體：大中小

來源：轉載

供稿：網友

ios數據存儲包括以下幾種存儲機制：

屬性列表
對象歸檔
SQLite3
CoreData
AppSettings
普通文件存儲

1、屬性列表

復制代碼代碼如下:

//  
//  Persistence1ViewController.h  
//  Persistence1  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import <UIKit/UIKit.h>  
#define kFilename @"data.plist"  
  
@interface Persistence1ViewController : UIViewController {  
    UITextField *filed1;  
    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  

復制代碼代碼如下:

//  
//  Persistence1ViewController.m  
//  Persistence1  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import "Persistence1ViewController.h"  
  
@implementation Persistence1ViewController  
@synthesize field1;  
@synthesize field2;  
@synthesize field3;  
@synthesize field4;  
  
//數據文件的完整路徑  
- (NSString *)dataFilePath {  
    //檢索Documents目錄路徑。第二個參數表示將搜索限制在我們的應用程序沙盒中  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    //每個應用程序只有一個Documents目錄  
    NSString *documentsDirectory = [paths objectAtIndex:0];  
    //創建文件名  
    return [documentsDirectory stringByAppendingPathComponent:kFilename];  
}  
  
//應用程序退出時，將數據保存到屬性列表文件  
- (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];  
}  
  
/* 
// 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.  
- (void)viewDidLoad {  
    [super viewDidLoad];  
    NSString *filePath = [self dataFilePath];  
    //檢查數據文件是否存在  
    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];  
    }  
    UIApplication *app = [UIApplication sharedApplication];  
    [[NSNotificationCenter defaultCenter] addObserver:self  
                                            selector:@selector(applicationWillResignActive:)  
                                            name:UIApplicationWillResignActiveNotification  
                                            object:app];  
    [super viewDidLoad];  
}  
  
  
/* 
// 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 {  
    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  

2、對象歸檔

復制代碼代碼如下:

//
// Fourlines.h
// Persistence2
//
// Created by liu lavy on 11-10-3.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import <Foundation/Foundation.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

復制代碼代碼如下:

//  
//  Fourlines.m  
//  Persistence2  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#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;  
  
#pragma mark NSCoding  
- (void)encodeWithCoder:(NSCoder *)aCoder {  
    [aCoder encodeObject:field1 forKey:kField1Key];  
    [aCoder encodeObject:field2 forKey:kField2Key];  
    [aCoder encodeObject:field3 forKey:kField3Key];  
    [aCoder encodeObject:field4 forKey:kField4Key];  
}  
  
-(id) initWithCoder:(NSCoder *)aDecoder {  
    if(self = [super init]) {  
        field1 = [[aDecoder decodeObjectForKey:kField1Key] retain];  
        field2 = [[aDecoder decodeObjectForKey:kField2Key] retain];  
        field3 = [[aDecoder decodeObjectForKey:kField3Key] retain];  
        field4 = [[aDecoder decodeObjectForKey:kField4Key] retain];  
    }  
    return self;  
}  
  
#pragma mark -  
#pragma mark NSCopying  
- (id) 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  

復制代碼代碼如下:

//  
//  Persistence2ViewController.h  
//  Persistence2  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import <UIKit/UIKit.h>  
#define kFilename @"archive"  
#define kDataKey @"Data"  
  
@interface Persistence2ViewController : UIViewController {  
    UITextField *filed1;  
    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  

復制代碼代碼如下:

//  
//  Persistence2ViewController.m  
//  Persistence2  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import "Persistence2ViewController.h"  
#import "Fourlines.h"  
  
@implementation Persistence2ViewController  
@synthesize field1;  
@synthesize field2;  
@synthesize field3;  
@synthesize field4;  
  
//數據文件的完整路徑  
- (NSString *)dataFilePath {  
    //檢索Documents目錄路徑。第二個參數表示將搜索限制在我們的應用程序沙盒中  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    //每個應用程序只有一個Documents目錄  
    NSString *documentsDirectory = [paths objectAtIndex:0];  
    //創建文件名  
    return [documentsDirectory stringByAppendingPathComponent:kFilename];  
}  
  
//應用程序退出時，將數據保存到屬性列表文件  
- (void)applicationWillResignActive:(NSNotification *)notification {  
    Fourlines *fourlines = [[Fourlines alloc] init];  
    fourlines.field1 = field1.text;  
    fourlines.field2 = field2.text;  
    fourlines.field3 = field3.text;  
    fourlines.field4 = field4.text;  
      
    NSMutableData *data = [[NSMutableData alloc] init];//用于存儲編碼的數據  
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];  
      
    [archiver encodeObject:fourlines forKey:kDataKey];  
    [archiver finishEncoding];  
    [data writeToFile:[self dataFilePath] atomically:YES];  
      
    [fourlines release];  
    [archiver release];  
    [data release];  
}  
  
/* 
 // 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.  
- (void)viewDidLoad {  
    [super viewDidLoad];  
    NSString *filePath = [self dataFilePath];  
    //檢查數據文件是否存在  
    if([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {  
          
        //從文件獲取用于解碼的數據  
        NSData *data = [[NSMutableData alloc] initWithContentsOfFile:[self dataFilePath]];  
        NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];  
          
        Fourlines *fourlines = [unarchiver decodeObjectForKey:kDataKey];  
        [unarchiver finishDecoding];  
          
        field1.text = fourlines.field1;  
        field2.text = fourlines.field2;  
        field3.text = fourlines.field3;  
        field4.text = fourlines.field4;  
          
        [unarchiver release];  
        [data release];  
    }  
    UIApplication *app = [UIApplication sharedApplication];  
    [[NSNotificationCenter defaultCenter] addObserver:self  
                                             selector:@selector(applicationWillResignActive:)  
                                             name:UIApplicationWillResignActiveNotification  
                                             object:app];  
    [super viewDidLoad];  
}  
  
  
/* 
 // 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 {  
    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  

3、SQLite

復制代碼代碼如下:

//  
//  Persistence3ViewController.h  
//  Persistence3  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import <UIKit/UIKit.h>  
#define kFilename @"data.sqlite3"  
  
@interface Persistence3ViewController : UIViewController {  
    UITextField *filed1;  
    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  

復制代碼代碼如下:

//  
//  Persistence3ViewController.m  
//  Persistence3  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import "Persistence3ViewController.h"  
#import <sqlite3.h>  
  
@implementation Persistence3ViewController  
@synthesize field1;  
@synthesize field2;  
@synthesize field3;  
@synthesize field4;  
  
//數據文件的完整路徑  
- (NSString *)dataFilePath {  
    //檢索Documents目錄路徑。第二個參數表示將搜索限制在我們的應用程序沙盒中  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    //每個應用程序只有一個Documents目錄  
    NSString *documentsDirectory = [paths objectAtIndex:0];  
    //創建文件名  
    return [documentsDirectory stringByAppendingPathComponent:kFilename];  
}  
  
//應用程序退出時，將數據保存到屬性列表文件  
- (void)applicationWillResignActive:(NSNotification *)notification {  
    sqlite3 *database;  
    if(sqlite3_open([[self dataFilePath] UTF8String], &database) != SQLITE_OK) {  
        sqlite3_close(database);  
        NSAssert(0, @"Failed to open database");  
    }  
      
    for(int i = 1; i <= 4; i++) {  
        NSString *fieldname = [[NSString alloc] initWithFormat:@"field%d", i];  
        UITextField *field = [self valueForKey:fieldname];  
        [fieldname release];  
          
        char *update = "INSERT OR REPLACE INTO FIELDS (ROW, FIELD_DATA) VALUES (?, ?);";  
        sqlite3_stmt *stmt;  
        //將SQL語句編譯為sqlite內部一個結構體(sqlite3_stmt),類似java JDBC的PreparedStatement預編譯  
        if (sqlite3_prepare_v2(database, update, -1, &stmt, nil) == SQLITE_OK) {  
            //在bind參數的時候,參數列表的index從1開始,而取出數據的時候,列的index是從0開始  
            sqlite3_bind_int(stmt, 1, i);  
            sqlite3_bind_text(stmt, 2, [field.text UTF8String], -1, NULL);  
        } else {  
            NSAssert(0, @"Error:Failed to prepare statemen");  
        }  
        //執行SQL文，獲取結果   
        int result = sqlite3_step(stmt);  
        if(result != SQLITE_DONE) {  
            NSAssert1(0, @"Error updating table: %d", result);  
        }  
        //釋放stmt占用的內存(sqlite3_prepare_v2()分配的）  
        sqlite3_finalize(stmt);  
    }  
    sqlite3_close(database);  
}  
  
/* 
 // 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.  
- (void)viewDidLoad {  
    [super viewDidLoad];  
    NSString *filePath = [self dataFilePath];  
    //檢查數據文件是否存在  
    if([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {  
        //打開數據庫  
        sqlite3 *database;  
        if(sqlite3_open([filePath UTF8String], &database) != SQLITE_OK) {  
            sqlite3_close(database);  
            NSAssert(0, @"Failed to open database");  
        }  
          
        //創建表  
        char *errorMsg;  
        NSString *createSQL =   
            @"CREATE TABLE IF NOT EXISTS FIELDS (ROW INTEGER PRIMARY KEY, FIELD_DATA TEXT);";  
        if(sqlite3_exec(database, [createSQL UTF8String], NULL, NULL, &errorMsg) != SQLITE_OK) {  
            sqlite3_close(database);  
            NSAssert(0, @"Error creating table: %s", errorMsg);  
        }  
  
        //查詢  
        NSString *query = @"SELECT ROW, FIELD_DATA FROM FIELDS ORDER BY ROW";  
        sqlite3_stmt *statement;  
        //設置nByte可以加速操作  
        if(sqlite3_prepare_v2(database, [query UTF8String], -1, &statement, nil) == SQLITE_OK) {  
            while (sqlite3_step(statement) == SQLITE_ROW) {//返回每一行  
                int row = sqlite3_column_int(statement, 0);  
                char *rowData = (char *)sqlite3_column_text(statement, 1);  
                  
                NSString *fieldName = [[NSString alloc] initWithFormat:@"field%d", row];  
                NSString *fieldValue = [[NSString alloc] initWithUTF8String:rowData];  
                  
                UITextField *field = [self valueForKey:fieldName];  
                field.text = fieldValue;  
                  
                [fieldName release];  
                [fieldValue release];  
            }  
            //釋放statement占用的內存(sqlite3_prepare()分配的）  
            sqlite3_finalize(statement);  
        }  
        sqlite3_close(database);  
    }  
      
      
    UIApplication *app = [UIApplication sharedApplication];  
    [[NSNotificationCenter defaultCenter] addObserver:self  
                                             selector:@selector(applicationWillResignActive:)  
                                                 name:UIApplicationWillResignActiveNotification  
                                               object:app];  
    [super viewDidLoad];  
}  
  
  
/* 
 // 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 {  
    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  

4、Core Data

復制代碼代碼如下:

//  
//  PersistenceViewController.h  
//  Persistence4  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import <UIKit/UIKit.h>  
  
  
@interface PersistenceViewController : UIViewController {  
    UITextField *filed1;  
    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;  
  
@end  

復制代碼代碼如下:

//  
//  PersistenceViewController.m  
//  Persistence4  
//  
//  Created by liu lavy on 11-10-3.  
//  Copyright 2011 __MyCompanyName__. All rights reserved.  
//  
  
#import "PersistenceViewController.h"  
#import "Persistence4AppDelegate.h"  
  
@implementation PersistenceViewController  
@synthesize field1;  
@synthesize field2;  
@synthesize field3;  
@synthesize field4;  
  
  
-(void) applicationWillResignActive:(NSNotification *)notification {  
    Persistence4AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];  
    NSManagedObjectContext *context = [appDelegate managedObjectContext];  
    NSError *error;  
    for(int i = 1; i <= 4; i++) {  
        NSString *fieldName = [NSString stringWithFormat:@"field%d", i];  
        UITextField *theField = [self valueForKey:fieldName];  
          
        //創建提取請求  
        NSFetchRequest *request = [[NSFetchRequest alloc] init];  
        //創建實體描述并關聯到請求  
        NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Line"  
                                                             inManagedObjectContext:context];  
        [request setEntity:entityDescription];  
          
        //設置檢索數據的條件  
        NSPredicate *pred = [NSPredicate predicateWithFormat:@"(lineNum = %d)", i];  
        [request setPredicate:pred];  
          
        NSManagedObject *theLine = nil;  
        ////檢查是否返回了標準匹配的對象，如果有則加載它，如果沒有則創建一個新的托管對象來保存此字段的文本  
        NSArray *objects = [context executeFetchRequest:request error:&error];  
        if(!objects) {  
            NSLog(@"There was an error");  
        }  
        //if(objects.count > 0) {  
        //  theLine = [objects objectAtIndex:0];  
        //} else {  
            //創建一個新的托管對象來保存此字段的文本  
            theLine = [NSEntityDescription insertNewObjectForEntityForName:@"Line"  
                                                    inManagedObjectContext:context];  
            [theLine setValue:[NSNumber numberWithInt:i] forKey:@"lineNum"];  
            [theLine setValue:theField.text forKey:@"lineText"];  
        //}  
        [request release];  
    }  
    //通知上下文保存更改  
    [context save:&error];  
      
}  
  
// The designated initializer.  Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.  
/* 
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
        // Custom initialization. 
    } 
    return self; 
} 
*/  
  
  
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.  
- (void)viewDidLoad {  
    Persistence4AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];  
      
    NSManagedObjectContext *context = [appDelegate managedObjectContext];  
    //創建一個實體描述  
    NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Line" inManagedObjectContext:context];  
    //創建一個請求，用于提取對象  
    NSFetchRequest *request = [[NSFetchRequest alloc] init];  
    [request setEntity:entityDescription];  
      
    //檢索對象  
    NSError *error;  
    NSArray *objects = [context executeFetchRequest:request error:&error];  
    if(!objects) {  
        NSLog(@"There was an error!");  
    }  
    for(NSManagedObject *obj in objects) {  
        NSNumber *lineNum = [obj valueForKey:@"lineNum"];  
        NSString *lineText = [obj valueForKey:@"lineText"];  
        NSString *fieldName = [NSString stringWithFormat:@"field%d", [lineNum integerValue]];  
        UITextField *textField = [self valueForKey:fieldName];  
        textField.text = lineText;  
    }  
    [request release];  
      
    UIApplication *app = [UIApplication sharedApplication];  
    [[NSNotificationCenter defaultCenter] addObserver:self   
                                             selector:@selector(applicationWillResignActive:)   
                                                 name:UIApplicationWillResignActiveNotification  
                                               object:app];  
    [super viewDidLoad];  
}  
  
/* 
// 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 {  
    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  