iPhone开发之SQLite

现在网站开发和软件开发，数据库的支持是少不了的；在iPhone开发中，作为数据持久化的解决方案中，SQLite是不错的选择，它既轻量占用资源少，又可以方便嵌入到程序中，在一些嵌入式设备中有着广泛使用。

SQLite提供了命令行工具sqlite3，创建创建库。

cjdx@~/Desktop$ sqlite3 school.sqlite3
SQLite version 3.6.12
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite>

创建student表

sqlite> create table student (key integer primary key, name text, age integer, birth date);

插入三条数据

sqlite> insert into student (name, age, birth) values ('zhangsan', 18, '1980-01-09');
sqlite> insert into student (name, age, birth) values ('lisi', 20, '1980-10-05');
sqlite> insert into student (name, age, birth) values ('wangwu', 28, '1985-12-20');

查询刚刚插入的数据

sqlite> select * from student;
1|zhangsan|18|1980-01-09
2|lisi|20|1980-10-05
3|wangwu|28|1985-12-20

SQLite函数知识准备

sqlite3_open 打开数据库
sqlite3_close 关闭数据库
sqlite3_prepare 预编译SQL语句
sqlite3_step 执行预编译后的SQL
sqlite3_finalize 释放资源

打开Xcode，创建iPhone项目，基于“Single View Application”，并命名为TestSQLite，把刚才创建的school.sqlite3添加项目“Supporting Files”目录。

先写些测试代码，看看sqlite能不能正常工作，在ViewController.m中添加如下代码：

// ViewController.m
 
#import "ViewController.h"
#import "/usr/include/sqlite3.h"
 
@implementation ViewController
 
...
 
#pragma mark - View lifecycle
 
- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    sqlite3 *db;
    char *szError = NULL;
    sqlite3_stmt *dbps;
 
    NSString *dbFile = [[NSBundle mainBundle] pathForResource:@"school" ofType:@"sqlite3"];
    if (sqlite3_open([dbFile UTF8String], &db) != SQLITE_OK) {
        NSLog(@"failed to open db.");
    }
 
    NSString *sql_insert = @"insert into student (name, age, birth) values ('testdata', 16, '1987-09-18')";
 
    if (sqlite3_exec(db, [sql_insert UTF8String], 0, 0, &szError) == SQLITE_OK) {
        NSLog(@"%d", sqlite3_changes(db));
    }
 
    NSString *sql_select = @"SELECT * FROM student";
 
    sqlite3_prepare_v2(db, [sql_select UTF8String], -1, &dbps, NULL);
    int nResult = sqlite3_step(dbps);
    for (int fld = 0; fld < sqlite3_column_count(dbps); fld++) {
        NSLog(@"%s", sqlite3_column_name(dbps, fld));
    }
 
    while (nResult != SQLITE_DONE) {
        NSLog(@"%s|%s|%s|%s", 
              sqlite3_column_text(dbps, 0),
              sqlite3_column_text(dbps, 1),
              sqlite3_column_text(dbps, 2),
              sqlite3_column_text(dbps, 3));
        nResult = sqlite3_step(dbps);
    }
 
    sqlite3_close(db);
}
...
@end

把sqlite3连接库添加到项目

输出结果：

2012-02-06 18:59:33.372 TestSQLite[4011:207] 1
2012-02-06 18:59:33.375 TestSQLite[4011:207] key
2012-02-06 18:59:33.377 TestSQLite[4011:207] name
2012-02-06 18:59:33.379 TestSQLite[4011:207] age
2012-02-06 18:59:33.380 TestSQLite[4011:207] birth
2012-02-06 18:59:33.384 TestSQLite[4011:207] 1|zhangsan|18|1980-01-09
2012-02-06 18:59:33.386 TestSQLite[4011:207] 2|lisi|20|1980-10-05
2012-02-06 18:59:33.387 TestSQLite[4011:207] 3|wangwu|28|1985-12-20
2012-02-06 18:59:33.405 TestSQLite[4011:207] 4|testdata|16|1987-09-18

在Objc中直接用SQLite的C API写，如果每个查询都这样，太繁琐了，而且也不OO，所以还是要封装一下的，这样就可以把先前学过的知识串起来，写个小程序，用TableView来显示数据，支持数据的输入、删除。

• ♥ 1.创建Student模型类
• ♥ 2.创建StudentDB类
• ♥ 3.创建TableViewController用来显示数据
• ♥ 4.创建添加数据界面和代码的实现
• ♥ 5.删除代码的实现

接下来就按照这个步骤，一步步实现这些功能。

创建Student模型类

// Student.h
 
#import <Foundation/Foundation.h>
 
@interface Student : NSObject
{
    int uniqueId;
    NSString *name;
    int age;
    NSDate *birth;
}
 
@property (nonatomic, assign) int uniqueId;
@property (nonatomic, retain) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, retain) NSDate *birth;
 
- (id)initWithUniqueId:(int)uniqueId name:(NSString *)name age:(int)age birth:(NSDate *)birth;
 
@end

// Student.m
 
#import "Student.h"
 
@implementation Student
 
@synthesize uniqueId, name, age, birth;
 
- (id)initWithUniqueId:(int)uniqueId name:(NSString *)name age:(int)age birth:(NSDate *)birth
{
    self = [super init];
    if (self) {
        self.uniqueId = uniqueId;
        self.name = name;
        self.age = age;
        self.birth = birth;
    }
 
    return self;
}
 
- (void)dealloc
{
    name = nil;
    birth = nil;
    [super dealloc];
}
 
@end

创建StudentDB类

StudentDB类是sqlite的简单封装，获取的数据被包装到Student类中，有点ORM的感觉，代码长的就不贴代码，只贴一些关键代码。

// StudentDB.m
 
#import "StudentDB.h"
#import "Student.h"
 
@implementation StudentDB
 
@synthesize db;
 
- (id)init
{
    self = [super init];
    if (self) {
        NSString *dbFile = [[NSBundle mainBundle] pathForResource:@"school" ofType:@"sqlite3"];
        if (sqlite3_open([dbFile UTF8String], &db) != SQLITE_OK) {
            NSLog(@"failed to open db.");
        }
    }
 
    return self;
}
 
-(int)getStudentsCount
{
...
}
 
- (NSMutableArray *)getAllStudent
{
    sqlite3_stmt *pStmt;
    NSMutableArray *studentArray = [[NSMutableArray alloc] init];
    NSString *sql = @"SELECT * FROM student;";
    sqlite3_prepare_v2(db, [sql UTF8String], -1, &pStmt, nil);
    while (SQLITE_ROW == sqlite3_step(pStmt)) {
        int uniqueId = sqlite3_column_int(pStmt, 0);
        NSString *name = [[NSString alloc] initWithUTF8String:(const char*)sqlite3_column_text(pStmt, 1)];
        int age = sqlite3_column_int(pStmt, 2);
        NSDateFormatter *formate = [[NSDateFormatter alloc] init];
        [formate setDateFormat:@"yyyy-MM-dd"];
        NSDate *birth= [formate dateFromString:[[NSString alloc] initWithUTF8String:(const char *)sqlite3_column_text(pStmt, 3)]];
        Student *student = [[Student alloc] initWithUniqueId:uniqueId name:name age:age birth:birth];
        [studentArray addObject:student];
        [formate release];
        [name release];
        [student release];
    }
 
    sqlite3_finalize(pStmt);
 
    return studentArray;
}
 
- (void)removeStudent:(Student *)person
{
...
}
 
- (void)addStudent:(Student *)person
{
...
}
 
- (void)dealloc
{
    sqlite3_close(db);
    [super dealloc];
}
 
@end

创建TableViewController用来显示数据

通过StudentDB类的getAllStudent方法获取所有学生的数组作为数据源

// StudentListViewController.h
 
#import <UIKit/UIKit.h>
 
@class StudentDB;
 
@interface StudentListViewController : UITableViewController
{
    StudentDB *db;
    NSMutableArray *students;
}
 
@end

#import "StudentListViewController.h"
#import "StudentDB.h"
#import "Student.h"
#import "AddStudentViewController.h"
 
 
@implementation StudentListViewController
 
- (void)viewDidLoad
{
    // 初始化db
    db = [[StudentDB alloc] init];
 
    [super viewDidLoad];
}
 
- (void)viewWillAppear:(BOOL)animated
{
	// 获取所有学生数据保存到students数组中
    students = [db getAllStudent];
    [self.tableView reloadData];
 
    [super viewWillAppear:animated];
}
 
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}
 
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
	// 返回行数
    return students.count;
}
 
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
 
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }
 
    // Configure the cell...
    Student *student = [students objectAtIndex:indexPath.row];
    cell.textLabel.text = student.name;
 
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd"];
    NSString *strBirth = [dateFormatter stringFromDate:student.birth];
    NSString *strDescription = [[NSString alloc] initWithFormat:@"年龄:%d 生日:%s", student.age,
                                [strBirth UTF8String]];
    [cell.detailTextLabel setText:strDescription];
    [dateFormatter release];
    [strDescription release];
 
    return cell;
}
 
- (void)dealloc
{
    [students release];
    [db release];
    [super dealloc];
}
 
@end

数据显示效果图：

创建添加数据界面和代码的实现

通过点击导航右边的的“+”号按钮来显示，录入学生资料界面，界面通过纯代码创建，点击导航栏右边的”Done”来完成录入数据工作，然后返回学生列表界面执行reloadData操作，这样新录入的数据就能显示出来了

// AddStudentViewController.m
 
// 执行添加数据到数据库中的操作，没有验证性操作
- (void)doneButtonPushed:(id)sender
{
    StudentDB *db = [[StudentDB alloc] init];
    NSString *strName = txtName.text;
    int age = [txtAge.text intValue];
    NSString *strBirth = txtBirth.text;
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd"];
 
    Student *student = [[Student alloc] initWithUniqueId:0 name:strName age:age birth:[dateFormatter dateFromString:strBirth]];
    [db addStudent:student];
    [student release];
    [db release];
    [dateFormatter release];
    [self.navigationController popViewControllerAnimated:YES];
}

删除代码的实现

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        Student *student = [students objectAtIndex:indexPath.row];
        //删除数据库中的数据
        [db removeStudent:student];
        //删除数组中的数据
        [students removeObjectAtIndex:indexPath.row];
        //删除TableView中的数据
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}