IOS SQLite数据库

《IOS SQLite数据库》要点：
本文介绍了IOS SQLite数据库，希望对您有用。如果有疑问，可以联系我们。

简介

在IOS中使用Sqlite来处理数据.如果你已经了解了SQL,那你可以很容易的掌握SQLite数据库的操作.

实例步调

1、创建一个简单的View based application

2、选择项目文件,然后选择目标,添加libsqlite3.dylib库到选择框架

3、通过选择" File-> New -> File... -> "选择 Objective C class 创建新文件,单击下一步

4、"sub class of"为NSObject",类命名为DBManager

5、选择创建

6、更新DBManager.h,如下所示

#import <Foundation/Foundation.h>#import <sqlite3.h>@interface DBManager : NSObject{ NSString *databasePath;}+(DBManager*)getSharedInstance;-(BOOL)createDB;-(BOOL) saveData:(NSString*)registerNumber name:(NSString*)name department:(NSString*)department year:(NSString*)year;-(NSArray*) findByRegisterNumber:(NSString*)registerNumber;@end

7、更新DBManager.m,如下所示

#import "DBManager.h"static DBManager *sharedInstance = nil;static sqlite3 *database = nil;static sqlite3_stmt *statement = nil;@implementation DBManager+(DBManager*)getSharedInstance{ if (!sharedInstance) { sharedInstance = [[super allocWithZone:NULL]init]; [sharedInstance createDB]; } return sharedInstance;}-(BOOL)createDB{ NSString *docsDir; NSArray *dirPaths;  // Get the documents directory dirPaths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory,NSUserDomainMask,YES);  docsDir = dirPaths[0]; // Build the path to the database file databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: @"student.db"]]; BOOL isSuccess = YES; NSFileManager *filemgr = [NSFileManager defaultManager];  if ([filemgr fileExistsAtPath: databasePath ] == NO) { const char *dbpath = [databasePath UTF8String];  if (sqlite3_open(dbpath,&database) == SQLITE_OK) { char *errMsg; const char *sql_stmt = "create table if not exists studentsDetail (regno integer primary key,name text,department text,year text)";  if (sqlite3_exec(database,sql_stmt,NULL,&errMsg) != SQLITE_OK) { isSuccess = NO; NSLog(@"Failed to create table"); } sqlite3_close(database); return isSuccess; } else { isSuccess = NO; NSLog(@"Failed to open/create database"); } }  return isSuccess;}- (BOOL) saveData:(NSString*)registerNumber name:(NSString*)name department:(NSString*)department year:(NSString*)year;{ const char *dbpath = [databasePath UTF8String];  if (sqlite3_open(dbpath,&database) == SQLITE_OK) {  NSString *insertSQL = [NSString stringWithFormat:@"insert into studentsDetail (regno,name,department,year) values ("%d","%@","%@")",[registerNumber integerValue],year];  const char *insert_stmt = [insertSQL UTF8String]; sqlite3_prepare_v2(database,insert_stmt,-1,&statement,NULL); if (sqlite3_step(statement) == SQLITE_DONE) { return YES; } else { return NO; } sqlite3_reset(statement); } return NO;}- (NSArray*) findByRegisterNumber:(NSString*)registerNumber{ const char *dbpath = [databasePath UTF8String];  if (sqlite3_open(dbpath,&database) == SQLITE_OK) { NSString *querySQL = [NSString stringWithFormat: @"select name,year from studentsDetail where regno="%@"",registerNumber];  const char *query_stmt = [querySQL UTF8String]; NSMutableArray *resultArray = [[NSMutableArray alloc]init]; if (sqlite3_prepare_v2(database,query_stmt,NULL) == SQLITE_OK) { if (sqlite3_step(statement) == SQLITE_ROW) {  NSString *name = [[NSString alloc] initWithUTF8String: (const char *) sqlite3_column_text(statement,0)]; [resultArray addObject:name]; NSString *department = [[NSString alloc] initWithUTF8String: (const char *) sqlite3_column_text(statement,1)]; [resultArray addObject:department]; NSString *year = [[NSString alloc]initWithUTF8String: (const char *) sqlite3_column_text(statement,2)]; [resultArray addObject:year]; return resultArray; } else{ NSLog(@"Not found"); return nil; } sqlite3_reset(statement); } } return nil;}

8、如图所示,更新ViewController.xib文件

9、为上述文本字段创建IBOutlets

10、为上述按钮创建IBAction

11、如下所示,更新ViewController.h

#import <UIKit/UIKit.h>#import "DBManager.h"@interface ViewController : UIViewController<UITextFieldDelegate>{ IBOutlet UITextField *regNoTextField; IBOutlet UITextField *nameTextField; IBOutlet UITextField *departmentTextField; IBOutlet UITextField *yearTextField; IBOutlet UITextField *findByRegisterNumberTextField; IBOutlet UIScrollView *myScrollView;}-(IBAction)saveData:(id)sender;-(IBAction)findData:(id)sender;@end

12、更新ViewController.m,如下所示

#import "ViewController.h"@interface ViewController ()@end@implementation ViewController- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *) nibBundleOrNil{ self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { // Custom initialization } return self;}- (void)viewDidLoad{ [super viewDidLoad]; // Do any additional setup after loading the view from its nib.}- (void)didReceiveMemoryWarning{ [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated.}-(IBAction)saveData:(id)sender{ BOOL success = NO; NSString *alertString = @"Data Insertion failed"; if (regNoTextField.text.length>0 &&nameTextField.text.length>0 && departmentTextField.text.length>0 &&yearTextField.text.length>0 ) { success = [[DBManager getSharedInstance]saveData: regNoTextField.text name:nameTextField.text department: departmentTextField.text year:yearTextField.text]; } else{ alertString = @"Enter all fields"; }  if (success == NO) { UIAlertView *alert = [[UIAlertView alloc]initWithTitle: alertString message:nil delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; }}-(IBAction)findData:(id)sender{ NSArray *data = [[DBManager getSharedInstance]findByRegisterNumber: findByRegisterNumberTextField.text]; if (data == nil) { UIAlertView *alert = [[UIAlertView alloc]initWithTitle: @"Data not found" message:nil delegate:nil cancelButtonTitle: @"OK" otherButtonTitles:nil]; [alert show]; regNoTextField.text = @""; nameTextField.text =@""; departmentTextField.text = @""; yearTextField.text =@""; } else{ regNoTextField.text = findByRegisterNumberTextField.text; nameTextField.text =[data objectAtIndex:0]; departmentTextField.text = [data objectAtIndex:1]; yearTextField.text =[data objectAtIndex:2]; }}#pragma mark - Text field delegate-(void)textFieldDidBeginEditing:(UITextField *)textField{ [myScrollView setFrame:CGRectMake(10,50,300,200)]; [myScrollView setContentSize:CGSizeMake(300,350)];}-(void)textFieldDidEndEditing:(UITextField *)textField{ [myScrollView setFrame:CGRectMake(10,350)];}-(BOOL) textFieldShouldReturn:(UITextField *)textField{ [textField resignFirstResponder]; return YES;}@end

输出

现在当我们运行应用法式时,我们就会获得下面的输出,我们可以在其中添加及查找学生的详细信息

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（编辑：李大同）

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