首页 > 代码库 > 数据库,单例的使用
数据库,单例的使用
数据库的使用,和单例的使用
MainViewController.m
#import "MainViewController.h" #import "DataBaseHandler.h" @interface MainViewController () @end @implementation MainViewController - (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. self.view.backgroundColor = [UIColor cyanColor]; //数据库的使用 //使用单例方法 DataBaseHandler *dbHandler = [DataBaseHandler shareInstance]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } /* #pragma mark - Navigation // In a storyboard-based application, you will often want to do a little preparation before navigation - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { // Get the new view controller using [segue destinationViewController]. // Pass the selected object to the new view controller. } */ @end
DataBaseHandler.h
#import <Foundation/Foundation.h> #import <sqlite3.h> #import "Student.h" //对所有数据库的操作都在这个类中处理 //把这个类写成单例类(在一个应用程序中,只会产生一个对象) @interface DataBaseHandler : NSObject { //创建一个数据指针,指向本地的数据库文件 sqlite3 *dbPoint; } //单例方法 + (DataBaseHandler *)shareInstance; //在进行数据库的增删改查操作之前,需要打开数据库(dbPoint跟本地的数据库文件连接起来) - (void)openDB; - (void)closeDB; //创建表 - (void)createTable; //添加 - (void)insertStudent:(Student *)student; //查询 - (NSArray *)selectAllStudents; @end
DataBaseHandler.m
#import "DataBaseHandler.h" @implementation DataBaseHandler + (DataBaseHandler *)shareInstance { //static 一个应用程序执行期间,只会执行一次 static DataBaseHandler *dbHandler = nil; if (dbHandler == nil) { //如果指针指向空地址,就创建一个对象 dbHandler = [[DataBaseHandler alloc] init]; [dbHandler openDB]; [dbHandler createTable]; } return dbHandler; } - (void)openDB { //打开数据库的函数 NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject]; //拼接一个数据库的文件路径 NSString *dbPath = [docPath stringByAppendingPathComponent:@"dataBase.db"]; //参数1:数据库文件的路径 参数2:数据库指针的地址 int result = sqlite3_open([dbPath UTF8String], &dbPoint); //SQLITE_OK查看错误信息 NSLog(@"%d", result); NSLog(@"%@", dbPath); } - (void)closeDB { sqlite3_close(dbPoint); } - (void)createTable { //执行SQL语句的函数 NSString *sql = [NSString stringWithFormat:@"create table student (name text, id integer primary key, age float)"]; //参数1:数据库的指针 //参数2:要执行的sql语句 //参数3: //参数4: //参数5: int result = sqlite3_exec(dbPoint, [sql UTF8String], NULL, NULL, NULL); NSLog(@"创建结果%d", result); } - (void)insertStudent:(Student *)student { NSString *sql = [NSString stringWithFormat:@"insert into student values(‘%@‘, %d, %f)",student.name,student.number, student.age]; int result = sqlite3_exec(dbPoint, [sql UTF8String], NULL, NULL, NULL); NSLog(@"执行结果%d", result); } - (NSArray *)selectAllStudents { //1.创建一个数据库指针的替身 //替身作为一个临时的数据库指针,保存所有对数据库的操作,最终确认无误后写入本地数据库 sqlite3_stmt *stmt = nil; NSString *sql = [NSString stringWithFormat:@"select * from student"]; //2.检查sql语句,准备执行 //作用:把替身和数据库指针连接起来 //参数1:数据库指针 //参数2:sql语句 //参数3:闲置sql语句的长度 (-1)为不限制 //参数4:替身的指针 int result = sqlite3_prepare_v2(dbPoint, [sql UTF8String], -1, &stmt, NULL); //对sql语句的检查结果进行判断 if (result == SQLITE_OK) { NSMutableArray *array = [NSMutableArray array]; //如果当符合SQL语句查询条件的结果有多行,就执行循环体的代码 while (sqlite3_setp(stmt) == SQLITE_ROW) { //参数1:替身 参数2:取得是第几列的值 const unsigned char* nameStr = sqlite3_column_text(stmt, 0); NSString *name = [NSString stringWithUTF8String:(const char*)nameStr]; //把拿到的nsstring数据给一个学生对象赋值 Student *stu = [[Student alloc] init]; stu.name = name; stu.number = sqlite3_column_int(stmt, 1); stu.age = sqlite3_column_double(stmt, 2); //把创建好的学生对象添加到数据中 [array addObject:stu]; [stu release]; } //释放替身的内存占用,将替身的所有操作应用到底层数据库文件 sqlite3_finalize(stmt); return array; } //如果失败,返回空值 sqlite3_finalize(stmt); return nil; } @end
Student.h
#import <Foundation/Foundation.h> @interface Student : NSObject @property (nonatomic , retain)NSString *name; @property (nonatomic , assign)NSInteger number; @property (nonatomic , assign)float age; @end
Student.m
#import "Student.h" @implementation Student - (void)dealloc { [_name release]; [super dealloc]; } @end
本文出自 “小刘_Blog” 博客,请务必保留此出处http://liuyafang.blog.51cto.com/8837978/1557038
数据库,单例的使用
声明:以上内容来自用户投稿及互联网公开渠道收集整理发布,本网站不拥有所有权,未作人工编辑处理,也不承担相关法律责任,若内容有误或涉及侵权可进行投诉: 投诉/举报 工作人员会在5个工作日内联系你,一经查实,本站将立刻删除涉嫌侵权内容。