iOS：面向对象的思想使用sqlite数据库

SQLite支持的常见数据类型如下所示。

–INTEGER 有符号的整数类型

–REAL 浮点类型

–TEXT 字符串类型,采用UTF-8和UTF-16字符编码

–BLOB 二进制大对象类型,能够存放任何二进制数据

 

(C语言中)使用步骤：

1.新建项目时,先导入系统框架(C语言). （libsqlite3）

 

2.头文件#import<sqlite3.h>

 

3. sqlite3_open(fileName.UTF8String, &_db); 打开或者创建一个数据

    *_db自己定义一个sqlite3的成员变量.进行增删改查时要用

 

4.sqlite3_exec(_db, sql, NULL, NULL,&error);  //不带结果集的语句，只是对表做操作，不会返回出结果

*该函数可进行insert,delete,update操作.

 

5.查询操作select. //带结果集的查询语句，会返回出结果，从表中查询到的数据都会放到stmt结构体中

*sqlite3_prepare_v2(_db, sql, -1, &stmt, NULL);做查询前准备,检测SQL语句是否正确.

*sqlite3_step(stmt) 提取查询到的数据,一次提取一条.//通过循环可以取出所有数据

*sqlite3_column_text(stmt, 0)取出第0列的数据.

 

6.关闭数据库 sqlite3_close(sqlite3 *);

 

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执行带参数的SQL语句

NSString *sqlStr = @"INSERT OR REPLACE INTO note (cdate,content) VALUES (?,?)";

sqlite3_stmt *statement;
//预处理过程,产生结果集
if (sqlite3_prepare_v2(db, [sqlStr UTF8String], -1, &statement, 

NULL) == SQLITE_OK)

 {

 NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
  NSString *nsdate = [dateFormatter stringFromDate:model.date]; 

  //绑定参数开始
  sqlite3_bind_text(statement, 1, [nsdate UTF8String], -1, NULL);  sqlite3_bind_text(statement, 2, [model.content UTF8String], 

-1,    NULL);

  //执行插入
if (sqlite3_step(statement) != SQLITE_DONE)

 {  

NSAssert(NO, @"插入数据失败。"); } 

 } 

}

//清理结果集,防止内存泄露

 sqlite3_finalize(statement);

单例模式：（这里主要用来保证初始化的数据库是唯一的，只要创建了一次，那么它就不会被再创建）

+ (NoteDAO*)sharedManager 

{ 

  static dispatch_once_t once; 

  dispatch_once(&once, ^{ 

  sharedManager = [[self alloc] init]; 

  [sharedManager   createEditableCopyOfDatabaseIfNeeded]; }

  );

   return sharedManager;

 }

举例代码如下：

Student.h

#import <Foundation/Foundation.h>

@interface Student : NSObject
@property (assign,nonatomic)NSInteger ID;
@property (copy,nonatomic)NSString *name;
@property (assign,nonatomic)NSInteger age;
@property (assign,nonatomic)char gender;
@property (assign,nonatomic)float math;
@property (assign,nonatomic)float english;
@property (assign,nonatomic)float chinese;
@end

Student.m

#import "Student.h"

@implementation Student
-(NSString*)description
{
    return [NSString stringWithFormat:@"ID:%ld,name:%@,age:%ld,gender:%c,math:%.2lf,english:%.2lf,chinese:%.2lf",_ID,_name,_age,_gender,_math,_english,_chinese];
}
@end

StudentDAO.h(对每一个实体类的数据库封装起来，就采用这种XXXDAO.h/m的命名风格)

#import <Foundation/Foundation.h>
#import <sqlite3.h>
@class Student;
@interface StudentDAO : NSObject
{
    sqlite3 *_db;
}
//单例的方法
+(StudentDAO*)shareManager;

//初始化数据库：创建表，添加数据
-(void)initDb;

//添加学生记录
-(BOOL)addStudent:(Student *)stu;

//删除学生记录
-(BOOL)deleteStudentByName:(NSString *)name;

//修改学生记录
-(BOOL)updateStudnet:(Student*)stu;

//查询学生记录
//1.查询全部
-(NSArray *)queryStudentAll;
//2.查询符合条件的
-(Student *)queryStudentByName:(NSString*)name;

@end

StudentDAO.m

#import "StudentDAO.h"
#import "Student.h"


static StudentDAO *instance = nil;
@implementation StudentDAO

//对象只创建一次
+(StudentDAO*)shareManager
{
    static dispatch_once_t once;
    dispatch_once(&once, ^{
        //只执行一次
        instance = [StudentDAO new];
        
        [instance initDb];
    });
     
    return instance;
}

//执行不返回结果集的sql语句
-(BOOL)execSql:(NSString *)sql
{
    char *errmsg = NULL;
    //增删改操作
    sqlite3_exec(_db, [sql UTF8String], NULL, NULL, &errmsg);
    
    if(errmsg)
    {
        return NO;
    }
    else
    {
        return YES;
    }
}
//创建数据库文件路径
-(NSString*)pathForDB
{
    NSArray *dirs = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentPath = [dirs lastObject];
    
    //NSLog(@"%@",documentPath);
    
    return [documentPath stringByAppendingPathComponent:@"student.db"];
}

//初始化数据库：创建表，添加数据
-(void)initDb
{
    //打开数据库
    //sqlite3_open(fileName.UTF8String,&_db);打开或创建一个数据
    //*_db自己定义一个sqlite3的成员变量.进行增删改查时要用
    if(sqlite3_open([[self pathForDB] UTF8String], &_db) == SQLITE_OK)
    {
        //创建学生表
        if([self execSql:@"create table student (id integer primary key autoincrement,name text,age integer,gender integer,math real,english real,chinese real)"])
        {
            //表中添加测试数据
            for(int i=0; i<5; i++)
            {
                Student *stu = [Student new];
                stu.name = [NSString stringWithFormat:@"stu%d",i+1];
                stu.age = 20+i;
                stu.gender = 'M';
                stu.math = 80+i;
                stu.english = 90+i;
                stu.chinese = 80+i;
                
                [self addStudent:stu];
            }
        }
        //关闭数据库
       sqlite3_close(_db);
    }
}

//添加学生记录
-(BOOL)addStudent:(Student *)stu
{
    NSString *insertSql = @"insert into student (name,age,gender,math,english,chinese) values(?,?,?,?,?,?)";
    
    //打开数据库
    if(sqlite3_open([[self pathForDB]UTF8String], &_db) == SQLITE_OK)
    {
        //准备结果集
        //提取数据一次一条
        sqlite3_stmt *Pstmt = NULL;
        //查询前准备，看是否正确
        if(sqlite3_prepare_v2(_db, [insertSql UTF8String], -1, &Pstmt, NULL) == SQLITE_OK)
        {
            //绑定参数
            sqlite3_bind_text(Pstmt, 1, [stu.name UTF8String], -1, NULL);
            sqlite3_bind_int(Pstmt, 2, (int)stu.age);
            sqlite3_bind_int(Pstmt, 3, stu.gender);
            sqlite3_bind_double(Pstmt, 4, stu.math);
            sqlite3_bind_double(Pstmt, 5, stu.english);
            sqlite3_bind_double(Pstmt, 6, stu.chinese);
            
            //执行SQL语句
            if(sqlite3_step(Pstmt) == SQLITE_DONE)
            {
                return YES;
            }
        }
        //清理结果集
        sqlite3_finalize(Pstmt);
        
        //关闭数据库
        sqlite3_close(_db);
    }
    return NO;
}

//删除学生记录
-(BOOL)deleteStudentByName:(NSString *)name
{
    NSString *sql = @"delete from student where name = ?";
    
    //打开数据库
    if(sqlite3_open([[self pathForDB]UTF8String], &_db) == SQLITE_OK)
    {
        //准备结果集
        sqlite3_stmt *Pstmt = NULL;
        if(sqlite3_prepare_v2(_db, [sql UTF8String], -1, &Pstmt, NULL)== SQLITE_OK)
        {
            //绑定参数
            sqlite3_bind_text(Pstmt, 1, [name UTF8String], -1, NULL);
            
            
            //执行SQL语句
            if(sqlite3_step(Pstmt) == SQLITE_DONE)
            {
                return YES;
            }
        }
        //清理结果集
        sqlite3_finalize(Pstmt);
        
        //关闭数据库
        sqlite3_close(_db);
    }
    return NO;
}

//修改学生记录
-(BOOL)updateStudnet:(Student*)stu
{
    NSString *sql = @"update student set math = ? where name = ?";
    
    //打开数据库
    if(sqlite3_open([[self pathForDB]UTF8String], &_db) == SQLITE_OK)
    {
        //准备结果集
        sqlite3_stmt *Pstmt = NULL;
        if(sqlite3_prepare_v2(_db, [sql UTF8String], -1, &Pstmt, NULL) == SQLITE_OK)
        {
            //绑定参数
            sqlite3_bind_double(Pstmt,1,stu.math);
            sqlite3_bind_text(Pstmt, 2, [stu.name UTF8String], -1, NULL);
            
            //执行SQL语句
            if(sqlite3_step(Pstmt) == SQLITE_DONE)
            {
                return YES;
            }
        }
        //清理结果集
        sqlite3_finalize(Pstmt);
        
        //关闭数据库
        sqlite3_close(_db);
    }
    return NO;
}

//查询学生记录
//1.查询全部
-(NSArray *)queryStudentAll
{
    NSMutableArray *arrayM = [NSMutableArray array];
    
    //打开数据库
    if(sqlite3_open([[self pathForDB]UTF8String], &_db) == SQLITE_OK)
    {
        //准备结果集
        sqlite3_stmt *Pstmt = NULL;
        if(sqlite3_prepare_v2(_db, "select * from student", -1, &Pstmt, NULL) == SQLITE_OK)
        {
            //遍历结果集
            while (sqlite3_step(Pstmt) == SQLITE_ROW)
            {
                Student *stu = [Student new];
                
                stu.ID = sqlite3_column_int(Pstmt, 0);
                stu.name = [NSString stringWithFormat:@"%s",sqlite3_column_text(Pstmt, 1)];
                stu.age = sqlite3_column_int(Pstmt, 2);
                stu.gender = sqlite3_column_int(Pstmt, 3);
                stu.math = sqlite3_column_double(Pstmt, 4);
                stu.english = sqlite3_column_double(Pstmt, 5);
                stu.chinese = sqlite3_column_double(Pstmt, 6);
                
                [arrayM addObject:stu];
            }
        }
        //清理结果集
        sqlite3_finalize(Pstmt);
        
        //关闭数据库
        sqlite3_close(_db);
    }
    return arrayM;
}
//2.查询符合条件的
-(Student *)queryStudentByName:(NSString*)name
{
    Student *stu;
    NSString *sql = @"select * from student where name = ?";
    
    //打开数据库
    if(sqlite3_open([[self pathForDB]UTF8String], &_db) == SQLITE_OK)
    {
        //准备结果集
        sqlite3_stmt *Pstmt = NULL;
        if(sqlite3_prepare_v2(_db, [sql UTF8String], -1, &Pstmt, NULL) == SQLITE_OK)
        {
            //绑定参数
            sqlite3_bind_text(Pstmt, 1, [name UTF8String], -1, NULL);
            
            //执行SQL语句
            if(sqlite3_step(Pstmt) == SQLITE_ROW)
            {
                stu = [Student new];
                
                stu.ID = sqlite3_column_int(Pstmt, 0);
                stu.name = [NSString stringWithFormat:@"%s",sqlite3_column_text(Pstmt, 1)];
                stu.age = sqlite3_column_int(Pstmt, 2);
                stu.gender = sqlite3_column_int(Pstmt, 3);
                stu.math = sqlite3_column_double(Pstmt, 4);
                stu.english = sqlite3_column_double(Pstmt, 5);
                stu.chinese = sqlite3_column_double(Pstmt, 6);
            }
        }
        
        //清理结果集
        sqlite3_finalize(Pstmt);
        
        //关闭数据库
        sqlite3_close(_db);
    }
    return stu;;
}
@end

ViewController.m

#import "ViewController.h"
#import "Student.h"
#import "StudentDAO.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //测试stuDAO
    //创建单例对象
    StudentDAO *stuDAO = [StudentDAO shareManager];
    
    
    //查询所有的记录
    NSArray *students = [stuDAO queryStudentAll];
    NSLog(@"%@",students);
    
    //删除一条记录
    [stuDAO deleteStudentByName:@"stu3"];
    
    //修改记录
    Student *stu = [Student new];
    stu.name = @"stu4";
    stu.math = 94.5f;
    [stuDAO updateStudnet:stu];
    
    
    //通过名字查询学生
    Student *stu2 = [stuDAO queryStudentByName:@"stu5"];
    NSLog(@"%@",stu2);
    
    //查询所有的记录
    students = [stuDAO queryStudentAll];
    NSLog(@"%@",students);
}
@end