IOS中数据存储 sqlite3 的应用, 知识点: 数据库句柄 , 单例模式运用, Services服务层,sqlite3_open, sqlite3_exec, sqlite3_prepare_v2,sqlite3_step等等

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#import "PersonManager.h"

#import <sqlite3.h>

#import "NSString+JH.h"

// 全局变量

static PersonManager *_instance;

@interface
PersonManager()

{

    // 全局的数据库句柄

    sqlite3 *_db;

}

@end

@implementation
PersonManager

#pragma mark - 单例的方法

+ (id)allocWithZone:(struct
_NSZone *)zone

{

    static
dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{

        _instance = [super
allocWithZone:zone];

    });

    return
_instance;

}

+ (instancetype)sharedPersonManager

{

    if
(_instance == nil) {

        _instance = [[PersonManager alloc] init];

    }

    return
_instance;

}

#pragma mark - 类方法

- (id)init

{

    self
= [super
init];

    // 懒加载数据库连接及创建数据表

    if
(self) {

        // 1. 打开数据库

        [self
openDB];

        // 2. 创建数据表

        [self
createTable];

    }

    return
self;

}

#pragma mark 打开数据库

- (void)openDB

{

    NSString
*dbPath = [@"T_Person.db"
appendDocumentDir];

    _db = NULL;

    if
(SQLITE_OK == sqlite3_open([dbPath UTF8String], &_db)) {

        NSLog(@"数据库打开成功");

    } else
{

        NSLog(@"数据库打开失败");

    }

}

#pragma mark 单步执行SQL

- (void)execSQL:(NSString
*)sql message:(NSString
*)message

{

    char
*errmsg = NULL;

    if
(SQLITE_OK == sqlite3_exec(_db, [sql UTF8String], NULL, NULL, &errmsg)) {

        NSLog(@"%@成功!", message);

    } else
{

        NSLog(@"%@失败 - %s", message, errmsg);

    }

}

#pragma mark 创建数据表

- (void)createTable

{

    NSString
*sql = @"CREATE TABLE IF NOT EXISTS T_Person (id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, name TEXT, gender INTEGER, age INTEGER, height REAL)";

    [self
execSQL:sql message:@"创建数据表"];

}

- (void)addPerson:(Person *)person

{<br> // 1. SQL

    NSString
*sql = [NSString
stringWithFormat:@"INSERT INTO T_Person (name, gender, age, height) VALUES (‘%@‘, %d, %d, %f)", person.name, person.gender, person.age, person.height];

    [self
execSQL:sql message:@"新增个人记录"];

}

// 2. 更新用户（关于主键，永远都不要去修改）

- (void)updatePerson:(Person *)person where: (NSStirng
*)where

{

   NSString
*sql =  [NSString
stringWithFormat:@"UPDATE  T_Person  SET name = ‘%@‘, gender = %d, age = %d, height = %f where %@", person.name, person.gender, person.age, person.height , where];

    [self
execSQL:sql message:@"更新个人记录"];

}

// 3. 删除用户，使用主键来删除指定用户

- (void)removePerson:(NSInteger)personID

{

    NSString
*sql =[NSString
stringWithFormat: @"delete * from T_Person where id =%@",personID];

   [self
execSQL:sql message:@"删除记录成功"];

}

// 4. 列表用户，查询所有用户

- (NSArray
*)allPersons

{

    NSString
*sql = @"SELECT id, name, age, gender, height FROM T_Person ORDER BY name";

    sqlite3_stmt *stmt = NULL;

    NSMutableArray
*arrayM = [NSMutableArray
array];

    NSMutableArray
*persons = nil;

    if
(SQLITE_OK == sqlite3_prepare_v2(_db, [sql UTF8String], -1, &stmt, NULL)) {

        persons = [NSMutableArray
array];

        while
(SQLITE_ROW == sqlite3_step(stmt)) {

            int
ID = sqlite3_column_int(stmt, 0);

            const
unsigned char
*name = sqlite3_column_text(stmt, 1);

            int
age = sqlite3_column_int(stmt, 2);

            int
gender = sqlite3_column_int(stmt, 3);

            CGFloat height = sqlite3_column_double(stmt, 4);

            // const unsigned char *直接输出看不出结果，需要转换

            NSString
*nameUTF8 = [NSString
stringWithUTF8String:(const
char *)name];

            Person *p = [Person personWithID:ID name:nameUTF8 age:age gender:gender height:height];

            [persons addObject:p];

        }

    } else
{

        NSLog(@"语法错误");

    }

    return
persons;

}

@end