Base de datos SQLite para iOS
Introducción
En iOS se usa Sqlite para manejar datos. Si ya conoces SQL, puedes dominar fácilmente las operaciones de la base de datos SQLite.
Pasos del ejemplo
1. Crea una aplicación simple basada en una vista (View based application)
2. Selecciona el archivo del proyecto, luego selecciona el target y agrega la biblioteca libsqlite3.dylib al framework seleccionado.
3. Selecciona "File -> New -> File... -> " y elige "Objective C class" para crear un nuevo archivo; haz clic en Siguiente.
4. Establece "Subclass of" en "NSObject" y nombra la clase como "DBManager".
5. Selecciona Crear.
6. Actualiza DBManager.h, como se muestra a continuación.
#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. Actualiza DBManager.m, como se muestra a continuación.
#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. Actualiza el archivo ViewController.xib como se muestra en la figura.
9. Crea IBOutlets para los campos de texto mencionados anteriormente.
10. Crea IBAction para los botones mencionados anteriormente.
11. Actualiza ViewController.h como se muestra a continuación.
#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. Actualiza ViewController.m como se muestra a continuación.
#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
Salida
Ahora cuando ejecutamos la aplicación, obtendremos la siguiente salida, en la que podemos agregar y buscar los detalles de los estudiantes.
