iOS - SQLite 数据库
SQLite 可以在 iOS 中用于处理数据。 它使用 sqlite 查询，这使那些了解 SQL 的人更容易。
涉及的步骤
步骤 1 − 创建一个简单的 View based application 基于视图的应用程序。
步骤 2 − 选择您的项目文件，然后选择目标，然后在选择框架中添加 libsqlite3.dylib 库。
步骤 3 − 通过选择文件创建一个新文件 File→ New → File... → 选择 Objective C class 并点击下一步。
步骤 4 − 将类命名为 DBManager，将 "sub class of" 命名为 NSObject。
步骤 5 − 选择创建。
步骤 6 − 更新 DBManager.h 如下 −
实例
#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
步骤 7 − 更新 DBManager.m 如下 −
实例
#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;
}
步骤 8 − 更新 ViewController.xib 文件如下 −
步骤 9 − 为上述文本字段创建 IBOutlets。
步骤 10 − 为上述按钮创建 IBAction。
步骤 11 − 更新 ViewController.h 如下 −
实例
#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
步骤 12 − 更新 ViewController.m 如下 −
实例
#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
当我们运行应用程序时，我们将获得以下输出，我们可以在其中添加和查找学生详细信息 −
