iOS 数据库持久化

-(void) addObserver{
    //当程序进入后台时执行操作
    UIApplication *app = [UIApplication sharedApplication];
    [[ NSNotificationCenter defaultCenter] addObserver: self
                                              selector:@selector(appwillresignActive) name:UIApplicationWillResignActiveNotification object:app];
}
-(void) appwillresignActive{
    NSLog(@"监听测试");
}

 头部引入

#import "sqlite3.h"

-(void) makeDBinfo{
    NSArray *documentsPaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    
    NSString *databaseFilePath=[[documentsPaths objectAtIndex:0] stringByAppendingPathComponent:@"mydb"];
    
   char *errorMsg;
     
    //打开或创建数据库
    sqlite3 *database;
    
    if (sqlite3_open([databaseFilePath UTF8String], &database)!=SQLITE_OK) {
        sqlite3_close(database); 
    }else {
        NSLog(@"open sqlite db ok.");
    }
    //创建数据库表
    
    const char *createSql=" create table if not exists persons (id integer primary key autoincrement,name text)";
    
    if (sqlite3_exec(database, createSql, NULL, NULL, &errorMsg)==SQLITE_OK)
    {
        NSLog(@"create table ok.");
    }else
   {
        //如果在多个地方使用errorMsg，那么每次使用完毕要清空一下字串，比如这样：
        NSLog(@"error: %s",errorMsg);
        sqlite3_free(errorMsg);
    }
       // 向表中插入记录
    const char *insertSql="insert into persons (name) values(\"张三\")";
    if (sqlite3_exec(database, insertSql, NULL, NULL, &errorMsg)==SQLITE_OK)
    {
        NSLog(@"insert ok.");
    }else
    {
        //如果在多个地方使用errorMsg，那么每次使用完毕要清空一下字串，比如这样：
        NSLog(@"error: %s",errorMsg);
        sqlite3_free(errorMsg);
    }
    
    //结果集的查询，需要用到statement：
        const char *selectSql="select id,name from persons where name = ? ";
        sqlite3_stmt *statement;
         
        if (sqlite3_prepare_v2(database, selectSql, -1, &statement, nil)==SQLITE_OK) {
            NSLog(@"select ok.");
            
            sqlite3_bind_text(statement, 1, "张三",-1,NULL);
            
            
            while (sqlite3_step(statement)==SQLITE_ROW) {
                int _id=sqlite3_column_int(statement, 0);
                NSString *name=[[NSString alloc] initWithCString:(char *)sqlite3_column_text(statement, 1) encoding:NSUTF8StringEncoding];
                NSLog(@"row>>id %i, name %@",_id,name);
            }
            
            sqlite3_finalize(statement);
        }
         sqlite3_close(database); 

}

删除表操作

constchar *sql_drop_table="drop table if exists t";

constchar *sql_create_table="create table t(id int primary key,msg varchar(128))";

sqlite3_exec(db,sql_drop_table,0,0,&errmsg);

sqlite3_exec(db,sql_create_table,0,0,&errmsg);

插入数据

sqlite3_exec(db,"insert into t(id,msg) values(1,'Ady Liu')",NULL,NULL,&errmsg);

预编译操作

int i = 0;

sqlite3_stmt *stmt;

char ca[255];

//prepare statement

sqlite3_prepare_v2(db,"insert into t(id,msg) values(?,?)",-1,&stmt,0);

for(i=10;i<20;i++){

    sprintf(ca,"HELLO#%i",i);

    sqlite3_bind_int(stmt,1,i);

    sqlite3_bind_text(stmt,2,ca,strlen(ca),NULL);

    sqlite3_step(stmt);

    sqlite3_reset(stmt);

}

sqlite3_finalize(stmt)

查询操作

不使用回调的查询操作

受影响的记录数

总结