IOS SQLite数据库（sqlite创建数据库）

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。

实例步骤

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, 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],
 name, department, 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, department, year from studentsDetail where
 regno=\"%@\"",registerNumber]; 
 const char *query_stmt = [querySQL UTF8String];
 NSMutableArray *resultArray = [[NSMutableArray alloc]init];
 if (sqlite3_prepare_v2(database,
 query_stmt, -1, &statement, 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, 50, 300, 350)];}-(BOOL) textFieldShouldReturn:(UITextField *)textField{
 [textField resignFirstResponder];
 return YES;}@end

输出

现在当我们运行应用程序时，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