IOS SQLite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