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基本数据持久性

发布时间：2020-12-12 20:29:30 所属栏目：百科 来源：网络整理
导读：获取Documents目录 [cpp] view plain copy NSArray*path=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES); NSString*documentsDirectory=[pathobjectAtIndex:0]; NSString*filename=[documentsDirectorystringByAppendingFo

获取Documents目录

[cpp] view plain copy
  1. NSArray*path=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
  2. NSString*documentsDirectory=[pathobjectAtIndex:0];
  4. NSString*filename=[documentsDirectorystringByAppendingFormat:@"thefFile.txt"];

获取tmp目录

copy
    NSString*tempPath=NSTemporaryDirectory();
  1. NSString*tempFile=[tempFilestringByAppendingFormat:@"tempFile.txt"];

属性列表序列化

许多应用程序都使用了属性列表，比如使用属性列表来指定程序首选项，只要字典或数组仅包含特定可序列化的对象，就可以将NSDictionary和NSarray实例写入属性列表及从属性列表创建他们。序列化对象已被转换为字节流，以便存储到文件中，或通过网络进行传输。尽管可以让任何对象可序列化，但是只能将某些对象放置到某个集合类（如NSDictionary或NSArray）中，然后使用该集合的writeToFile方法将他们存储到属性列表

如果你打算使用属性列表持久保存程序数据，则可以使用NSArray或NDDirectionary容纳需要持久化的数据，假设你放到NSArray或NSDirectionary的所有对象都是可序列化的对象，则可以通过字典或数组实例调用writeToFile:atnomically:方法来编写属性列表

copy
    [myArraywriteToFile:@"/some/file/location/output.plist"atomically:YES];

1、新建single view application

2、打开viewController.xib，添加控件如图


2、修改控制器

copy
    #import<UIKit/UIKit.h>
  1. #definekFilename@"data.plist"
  2. @interfaceViewController:UIViewController
  3. {
  4. IBOutletUITextField*field1;
  5. IBOutletUITextField*field2;
  6. IBOutletUITextField*field3;
  7. IBOutletUITextField*field4;
  8. }
  9. @property(nonatomic,retain)UITextField*field1;
  10. @property(nonatomic,retain)UITextField*field2;
  12. -(NSString*)dataFilePath;
  13. -(void)applicationWillTerminate:(NSNotification*)notification;
  14. @end

copy
    @implementationViewController
  1. @synthesizefield1;
  2. @synthesizefield2;
  3. @synthesizefield3;
  4. @synthesizefield4;
  5. -(NSString*)dataFilePath
  6. {
  7. NSArray*path=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,YES);
  8. return[documentsDirectorystringByAppendingFormat:@"thefFile.txt"];
  9. void)applicationWillTerminate:(NSNotification*)notifaction
  10. NSMutableArray*array=[[NSMutableArrayalloc]init];
  11. [arrayaddObject:field1.text];
  12. [arrayaddObject:field2.text];
  13. [arrayaddObject:field3.text];
  14. [arrayaddObject:field4.text];
  15. [arraywriteToFile:[selfdataFilePath]atomically:YES];
  16. [arrayrelease];
  17. }
  18. -(void)viewDidLoad
  19. NSString*filePath=[selfdataFilePath];
  20. if([[NSFileManagerdefaultManager]fileExistsAtPath:filePath]){
  21. NSArray*array=[[NSArrayalloc]initWithContentsOfFile:filePath];
  22. field1.text=[arrayobjectAtIndex:0];
  23. field2.text=[arrayobjectAtIndex:1];
  24. field3.text=[arrayobjectAtIndex:2];
  25. field4.text=[arrayobjectAtIndex:3];
  26. UIApplication*app=[UIApplicationsharedApplication];
  27. [[NSNotificationCenterdefaultCenter]addObserver:selfselector:@selector(applicationWillTerminate:)name:UIApplicationWillTerminateNotificationobject:app];
  28. [superviewDidLoad];
  29. void)dealloc{
  30. [field1release];
  31. [field2release];
  32. [field3release];
  33. [field4release];
  34. [superdealloc];
  35. @end

3、重新打开.xib 按下Control的同时，将File's Owner图标拖放到第一个文本字段，选择field1，第二个连接到field2 ......

对象归档

[csharp] copy
    #definekField1Key@"Field1"
  1. #definekField2Key@"Field2"
  2. #definekField3Key@"Field3"
  3. #definekField4Key@"Field4"
  5. #import<UIKit/UIKit.h>
  6. @interfaceFourLines:NSObject<NSCoding,NSCopying>
  7. NSString*field1;
  8. NSString*field2;
  9. NSString*field3;
  10. NSString*field4;

copy
    @implementationFourLines
  1. void)encodeWithCoder:(NSCoder*)aCoder
  2. [aCoderencodeObject:field1forKey:kField1Key];
  3. [aCoderencodeObject:field2forKey:kField2Key];
  4. [aCoderencodeObject:field3forKey:kField3Key];
  5. [aCoderencodeObject:field4forKey:kField4Key];
  6. -(id)initWithCoder:(NSCoder*)aDecoder
  7. if(self=[superinit]){
  8. self.field1=[aDecoderdecodeObjectForKey:kField1Key];
  9. self.field2=[aDecoderdecodeObjectForKey:kField2Key];
  10. self.field3=[aDecoderdecodeObjectForKey:kField3Key];
  11. self.field4=[aDecoderdecodeObjectForKey:kField4Key];
  12. returnself;
  13. -(id)copyWithZone:(NSZone*)zone
  14. FourLines*copy=[[[selfclass]allocWithZone:zone]init];
  15. field1=[self.field1copy];
  16. field2=[self.field2copy];
  17. field3=[self.field3copy];
  18. field4=[self.field4copy];
  19. returncopy;
  20. @end

copy
    #definekFilename@"archive"
  1. #definekDataKey@"Data"
  2. interfacePersistenceViewController:UIViewController
  3. IBOutletUITextField*field1;
  4. IBOutletUITextField*field2;
  5. IBOutletUITextField*field3;
  6. IBOutletUITextField*field4;
  9. -(NSString*)dataFilePath;
  10. void)applicationWillTerminate:(NSNotification*)notifacation;
  11. copy
      #import"ViewController.h"
    1. #import"FourLines.h"
    2. @implementationPersistenceViewController
    3. return[documentsDirectorystringByAppendingPathComponent:kFilename];
    4. void)applicationWillTerminate:(NSNotification*)notifacation
    5. FourLines*fourLines=[[FourLinesalloc]init];
    6. fourLines.field1=field1.text;
    7. fourLines.field2=field2.text;
    8. fourLines.field3=field3.text;
    9. fourLines.field4=field4.text;
    10. NSMutableData*data=[[NSMutableDataalloc]init];
    11. NSKeyedArchiver*archiver=[[NSKeyedArchiveralloc]initForWritingWithMutableData:data];
    12. [archiverencodeObject:fourLinesforKey:kDataKey];
    13. [archiverfinishEncoding];
    14. [datawriteToFile:[selfdataFilePath]atomically:YES];
    15. [fourLinesrelease];
    16. [archiverrelease];
    17. [datarelease];
    18. NSData*data=[[NSMutableDataalloc]initWithContentsOfFile:[selfdataFilePath]];
    19. NSKeyedUnarchiver*unarchiver=[[NSKeyedUnarchiveralloc]initForReadingWithData:data];
    20. FourLines*fourLines=[unarchiverdecodeObjectForKey:kDataKey];
    21. field1.text=fourLines.field1;
    22. field2.text=fourLines.field2;
    23. field3.text=fourLines.field3;
    24. field4.text=fourLines.field4;
    25. [unarchiverrelease];
    26. UIApplication*app=[UIApplicationsharedApplication];
    27. [[NSNotificationCenterdefaultCenter]addObserver:selfselector:@selector(applicationWillTerminate:)name:UIApplicationWillTerminateNotificationobject:app];
    28. [superviewDidLoad];
    29. void)dealloc{
    30. [field1release];
    31. [field2release];
    32. [field3release];
    33. [field4release];
    34. [superdealloc];
    35. @end

    SQLite3

    打开数据库

    sqlite3 *database;

    int result = sqlite3_open("/path/to/database/file",&database);

    如果result等于SQLITE_OK，则表示数据库已经成功打开。SQLite3是采用可以移植的C，所有它不知道什么是NSString，所幸，，有一个NSString方法，该方法从NSString实例生成C字符串

    char *cStringPath = [pathString UTF8String];

    关闭数据库

    sqlite3_close(database)

    创建表


    查询


    结果集


    copy
      #import"/usr/include/sqlite3.h"
    1. #definekFilename@"data.sqlite3"
    2. sqlite3*database;
    3. copy
        for(inti=1;i<=4;i++){
      1. NSString*fieldName=[[NSStringalloc]initWithFormat:@"field%d",i];
      2. UITextField*field=[selfvalueForKey:fieldName];
      3. [fieldNamerelease];
      4. NSString*update=[[NSStringalloc]initWithFormat:@"insertorreplaceintofields(row,field_data)values(%d,'%@');",i,field.text];
      5. char*errorMsg;
      6. if(sqlite3_exec(database,[updateUTF8String],NULL,&errorMsg)!=SQLITE_OK){
      7. NSAssert(0,@"Errorupdatingtable:%s",errorMsg);
      8. sqlite3_free(errorMsg);
      9. sqlite3_close(database);
      10. if(sqlite3_open([[selfdataFilePath]UTF8String],&database)!=SQLITE_OK){
      11. NSAssert(0,@"");
      12. NSString*createSQL=@"createtableifnotexistfields(rowintegerprimarykey,field_datatext);";
      13. sqlite3_close(database);
      14. "");
      15. NSString*query=@"selectrow,field_datafromfieldsorderbyrow";
      16. sqlite3_stmt*statement;
      17. if(sqlite3_prepare_v2(database,[queryUTF8String],-1,&statement,nil)==SQLITE_OK){
      18. while(sqlite3_step(statement)==SQLITE_OK){
      19. introw=sqlite3_column_int(statement,0);
      20. char*rowData=(char*)sqlite3_column_text(statement,1);
      21. NSString*fieldValue=[[NSStringalloc]initWithUTF8String:rowData];
      22. UITextField*field=[selfvalueForKey:fieldName];
      23. field.text=fieldValue;
      24. [fieldValuerelease];
      25. sqlite3_finalize(statement);
      26. @end

      （编辑：李大同）

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