SQLite的简单封装

//
//  StudentTool.h
//  SQLite的封装
//  学生数据的CRUD

#import <Foundation/Foundation.h>

@class Student;

@interface StudentTool : NSObject
+ (BOOL)addStudent:(Student *)student;
/**
*  获得所有学生
*
*  @return 数组中装着都说Student模型
*/
+ (NSArray *)students;
@end

//
//  StudentTool.m
//  SQLite的封装

#import "StudentTool.h"
#import "Student.h"
#import <sqlite3.h>

@implementation StudentTool

/**
*  全局变量
static的作用：能保证 _db 这个变量只被StudentTool.m直接访问
*/
static sqlite3 *_db;

+ (void)initialize
{
//0.获取沙盒中的数据库文件名
NSString *filename = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"student.sqlite"];

//1.创建(打开)数据库(如果数据库不存在,会自动创建)
int result = sqlite3_open(filename.UTF8String, &_db);
if (result == SQLITE_OK) {
NSLog(@"成功打开数据库");

//3.建表
const char *sql = "create table if not exists t_student (id integer primary key autoincrement,name text,age integer);";
char *errorMesg = NULL;
int result = sqlite3_exec(_db, sql, NULL, NULL, &errorMesg);
if (result == SQLITE_OK) {
NSLog(@"成功创建t_student表");
}else{
NSLog(@"创建t_student表失败:%s",errorMesg);
}
}else{
NSLog(@"打开数据库失败");
}
}

/**
*  添加学生
*
*  @param student 需要添加的学生
*/
+ (BOOL)addStudent:(Student *)student
{
NSString *sql = [NSString stringWithFormat:@"insert into t_student (name,age) values ('%@',%d);",student.name,student.age];

char *errorMesg = NULL;
int result = sqlite3_exec(_db, sql.UTF8String, NULL, NULL, &errorMesg);

return result == SQLITE_OK;
}

+ (NSArray *)students
{
//0.定义数组
NSMutableArray *students = nil;

//1.定义sql语句
const char *sql = "select id,name,age form t_student;";

//2.定义一个stmt存放结果集
sqlite3_stmt *stmt = NULL;

//3.检测SQL语句的合法性
int ressult = sqlite3_prepare_v2(_db, sql, -1, &stmt, NULL);
if (ressult == SQLITE_OK) {
NSLog(@"查询语句合法");
students = [NSMutableArray array];

//4.执行SQL语句
int stepResult = sqlite3_step(stmt);
while  (stepResult == SQLITE_ROW) {

Student *student = [[Student alloc] init];

//获得第0列的id
student.ID = sqlite3_column_int(stmt, 0);
//获得第1列的name
const unsigned char *sname = sqlite3_column_text(stmt, 1);
student.name = [NSString stringWithUTF8String:(const char *)sname];
//获得第2列的age
student.age = sqlite3_column_int(stmt, 2);

//添加到数组
[students addObject:student];
}
}else{
NSLog(@"查询语句非法");
}

return students;
}

@end

//
//  Student.h
//  SQLite的封装
//  学生模型

#import <Foundation/Foundation.h>

@interface Student : NSObject
/**
*  学生的id
*/
@property(nonatomic,assign) int ID;
/**
*  学生姓名
*/
@property(nonatomic,copy) NSString *name;
/**
*  学生的年龄
*/
@property(nonatomic,assign) int age;
@end

//
//  ViewController.m
//  SQLite的封装

#import "ViewController.h"
#import "StudentTool.h"
#import "Student.h"

@interface ViewController ()
- (IBAction)insert;
- (IBAction)query;

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}

- (IBAction)insert {
//添加30条数据

for (int i=0; i<30; i++) {
//创建学生
Student *student = [[Student alloc] init];
student.name = [NSString stringWithFormat:@"jack-%d",arc4random()%100];
student.age = arc4random()%100;

//添加学生
BOOL result = [StudentTool addStudent:student];
if (result) {
NSLog(@"添加成功");
}
}
}

- (IBAction)query {
NSArray *students = [StudentTool students];

for (Student *stu in students) {
NSLog(@"%d %@ %d",stu.ID,stu.name,stu.age);
}
}
@end