iOS数据持久化（二）SQLite

一、什么是SQLite

　　SQLite是一款轻型的嵌入式数据库，它占用资源非常的低，处理速度快，非常适合用于移动端开发。

二、使用

　　创建DataBaseHandle.h   &    DataBaseHandle.m

　　

DataBaseHandle.h

#import <Foundation/Foundation.h>
#import "Student.h"
@interface DataBaseHandle : NSObject
+ (DataBaseHandle *)shareDataBase;
- (void)openDB;
- (void)closeDB;
//添加数据
- (void)insertNewStudent:(Student *)student;
/**
 *  根据学号查询学生
 */
- (Student *)selectStudentWithNumber:(NSInteger)number;
/**
 *  查询表中所有数据
 */
- (NSMutableArray *)selectAllStudents;
/**
 *  根据学号删除
 */
- (void)deleteStudentWithNumber:(NSInteger)number;
- (void)updateStudent:(NSString *)gender WithNumber:(NSInteger)number;
@end

DataBaseHandle.m

+ (DataBaseHandle *)shareDataBase {
    @synchronized (self){
        if (handle == nil) {
            handle = [[DataBaseHandle alloc] init];
            
//            [handle closeDB];
        }
    }
    return handle;
}
sqlite3 *db = nil;

　　打开数据库

- (void)openDB {
    NSString *str = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)firstObject];
    NSString *path = [str stringByAppendingPathComponent:@"student.sqlite"];
    NSLog(@"%@",path);
    //打开数据库
    //UTF8String 将oc字符串转化为C语言字符串

    //方法执行完会返回一个数据库对象，这个对象已被初始化
    int result = sqlite3_open([path UTF8String], &db);
    //如果等于SQLITE_OK说明sql语句执行成功
    if (result == SQLITE_OK) {
        NSLog(@"数据库打开成功");
        //创建表格
        NSString *sqlString = @"create table if not exists Student (number integer primary key autoincrement,name text,gender text,age integer)";
          int result =  sqlite3_exec(db, [sqlString UTF8String], NULL, NULL, NULL);
        if (result == SQLITE_OK) {
            NSLog(@"见表成功");
        }
    } else {
        NSLog(@"数据库打开失败");
    }
}

　　关闭数据库

- (void)closeDB {
    int result = sqlite3_close(db);
    if (result == SQLITE_OK) {
        NSLog(@"关闭成功");
    }else {
        NSLog(@"关闭失败");
    }
}

　　插入数据

- (void)insertNewStudent:(Student *)student {
    [self openDB];
    //准备sql语句
    NSString *sqlString = @"insert into Student (name,gender, age) values (?, ?, ?)";
    /*第一个参数，数据库指针，
     第二个参数，sql语句
     第三个参数，sql语句的长度，写成-1，自动计算
     第四个参数，创建管理sql语句的类，statement
     第五个参数，预留参数
     */
    sqlite3_stmt *stmt = nil;
    int result = sqlite3_prepare_v2(db, [sqlString UTF8String], -1, &stmt, NULL);
    if (result == SQLITE_OK) {
        NSLog(@"添加语句成功");
        //绑定参数
        //绑定的参数：1.管理类指针，2.第几个问号，3.绑定的数据， 4.绑定数据的长度 -1   5.
        sqlite3_bind_text(stmt, 1, [student.name UTF8String], -1, NULL);
        sqlite3_bind_text(stmt, 2, [student.gender UTF8String], -1, NULL);
        sqlite3_bind_int(stmt, 3, (int)student.age);
        /**/
        sqlite3_step(stmt);
    } else {
        NSLog(@"添加语句失败");
    }
    sqlite3_finalize(stmt);
    [self closeDB];
}

　　查询数据

- (NSMutableArray *)selectAllStudents {
    [self openDB];
    NSString *sqlString = @"select * from student";
    sqlite3_stmt *stmt = nil;
    int result = sqlite3_prepare_v2(db, [sqlString UTF8String], -1, &stmt, nil);
    if (result == SQLITE_OK) {
        NSLog(@"查询全部成功");
        //循环的条件:下一行还有数据，这时就能一直循环下去
        NSMutableArray *array = [NSMutableArray arrayWithCapacity:0];
        while (sqlite3_step(stmt) == SQLITE_ROW) {
            NSString *name = [NSString stringWithUTF8String:(const char *)sqlite3_column_text(stmt, 1)];
            NSString *gender = [NSString stringWithUTF8String:(const char *)sqlite3_column_text(stmt, 2)];
            NSInteger age = sqlite3_column_int(stmt, 3);
            
            Student *stu = [[Student alloc] init];
            stu.name = name;
            stu.age = age;
            stu.gender = gender;
            [array addObject:stu];
            [stu release];
        }
        sqlite3_finalize(stmt);
        [self closeDB];

        return array;
    } else {
        NSLog(@"error");
        return nil;
    }
}

　　

- (Student *)selectStudentWithNumber:(NSInteger)number {
    [self openDB];
    
    NSString *sqlString = @"select * from Student where number = ?";
    
    sqlite3_stmt *stmt = nil;
    int result = sqlite3_prepare_v2(db, [sqlString UTF8String], -1, &stmt, NULL);
    if (result == SQLITE_OK) {
        NSLog(@"查询成功");
        //绑定参数
        sqlite3_bind_int(stmt, 1, (int)number);
        
        Student *student = [[[Student alloc] init]autorelease];
        while (sqlite3_step(stmt) == SQLITE_ROW) {
            student.name = [NSString stringWithUTF8String:(const char *)sqlite3_column_text(stmt, 1)];
            student.gender = [NSString stringWithUTF8String:(const char *)sqlite3_column_text(stmt, 2)];
            student.age = sqlite3_column_int(stmt, 3);
        }
        sqlite3_finalize(stmt);
        [self closeDB];
        return student;
        
    } else {
        NSLog(@"不OK");
        return nil;
    }
}

　　删除数据

- (void)deleteStudentWithNumber:(NSInteger)number {
    [self openDB];
    NSString *sqlString = @"delete from Student where number = ?";
    sqlite3_stmt *stmt = nil;
    int result = sqlite3_prepare_v2(db, [sqlString UTF8String], -1, &stmt, NULL);
    if (result == SQLITE_OK) {
        sqlite3_bind_int(stmt, 1, (int)number);
        //执行sql语句
        sqlite3_step(stmt);
    }
    //释放stmt的内存资源
    sqlite3_finalize(stmt);
    
    [self closeDB];
}

　　修改数据

- (void)updateStudent:(NSString *)gender WithNumber:(NSInteger)number {
    [self openDB];
    
    NSString *sqlString = @"update Student set gender = ? where number = ?";
    sqlite3_stmt *stmt = nil;
    int result = sqlite3_prepare_v2(db, [sqlString UTF8String], -1, &stmt, NULL);
    
    if (result == SQLITE_OK) {
        sqlite3_bind_int(stmt, 2, (int)number);
        
        sqlite3_step(stmt);
    }
    sqlite3_finalize(stmt);
    [self closeDB];
}