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=; i<; i++)
             {
                 Student *stu = [Student new];
                 stu.name = [NSString stringWithFormat:@"stu%d",i+];
                 stu.age = +i;
                 stu.gender = 'M';
                 stu.math = +i;
                 stu.english = +i;
                 stu.chinese = +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], -, &Pstmt, NULL) == SQLITE_OK)
         {
             //绑定参数
             sqlite3_bind_text(Pstmt, , [stu.name UTF8String], -, NULL);
             sqlite3_bind_int(Pstmt, , (int)stu.age);
             sqlite3_bind_int(Pstmt, , stu.gender);
             sqlite3_bind_double(Pstmt, , stu.math);
             sqlite3_bind_double(Pstmt, , stu.english);
             sqlite3_bind_double(Pstmt, , 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], -, &Pstmt, NULL)== SQLITE_OK)
         {
             //绑定参数
             sqlite3_bind_text(Pstmt, , [name UTF8String], -, 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], -, &Pstmt, NULL) == SQLITE_OK)
         {
             //绑定参数
             sqlite3_bind_double(Pstmt,,stu.math);
             sqlite3_bind_text(Pstmt, , [stu.name UTF8String], -, 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", -, &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, );
                 stu.name = [NSString stringWithFormat:@"%s",sqlite3_column_text(Pstmt, )];
                 stu.age = sqlite3_column_int(Pstmt, );
                 stu.gender = sqlite3_column_int(Pstmt, );
                 stu.math = sqlite3_column_double(Pstmt, );
                 stu.english = sqlite3_column_double(Pstmt, );
                 stu.chinese = sqlite3_column_double(Pstmt, );

                 [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], -, &Pstmt, NULL) == SQLITE_OK)
         {
             //绑定参数
             sqlite3_bind_text(Pstmt, , [name UTF8String], -, NULL);

             //执行SQL语句
             if(sqlite3_step(Pstmt) == SQLITE_ROW)
             {
                 stu = [Student new];

                 stu.ID = sqlite3_column_int(Pstmt, );
                 stu.name = [NSString stringWithFormat:@"%s",sqlite3_column_text(Pstmt, )];
                 stu.age = sqlite3_column_int(Pstmt, );
                 stu.gender = sqlite3_column_int(Pstmt, );
                 stu.math = sqlite3_column_double(Pstmt, );
                 stu.english = sqlite3_column_double(Pstmt, );
                 stu.chinese = sqlite3_column_double(Pstmt, );
             }
         }

         //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