SQLite 封装

记得要添加framework:libsqlite3.dylib 我在看的时候还有一个libsqlite3.0.dylib。应该后面的那个版本更新一点。

我现在要使用SQLite3.0创建一个数据库，然后在数据库中创建一个表格。

首先要引入SQLite3.0的lib库。然后包含头文件#import <sqlite3.h>

【1】打开数据库，如果没有，那么创建一个

sqlite3* database_;

-(BOOL) open{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"mydb.sql"];
NSFileManager *fileManager = [NSFileManager defaultManager];
BOOL find = [fileManager fileExistsAtPath:path];

//找到数据库文件mydb.sql
if (find) {
NSLog(@"Database file have already existed.");
if(sqlite3_open([path UTF8String],&database_) != SQLITE_OK) {
sqlite3_close(database_);
NSLog(@"Error: open database file.");
return NO;
}
return YES;
}
if(sqlite3_open([path UTF8String],&database_) == SQLITE_OK) {
bFirstCreate_ = YES;
[selfcreateChannelsTable:database_];//在后面实现函数createChannelsTable

return YES;
} else {
sqlite3_close(database_);
NSLog(@"Error: open database file.");
return NO;
}
return NO;
}

【2】创建表格

//创建表格，假设有五个字段，（id，cid，title，imageData ，imageLen ）

//说明一下，id为表格的主键，必须有。

//cid，和title都是字符串，imageData是二进制数据，imageLen 是该二进制数据的长度。
- (BOOL) createChannelsTable:(sqlite3*)db{
char *sql = "CREATE TABLE channels (id integer primary key,
cid text,
title text,
imageData BLOB,
imageLen integer)";
sqlite3_stmt *statement;
if(sqlite3_prepare_v2(db,sql,-1,&statement,nil) != SQLITE_OK) {
NSLog(@"Error: failed to prepare statement:create channels table");
return NO;
}
int success = sqlite3_step(statement);
sqlite3_finalize(statement);
if ( success != SQLITE_DONE) {
NSLog(@"Error: failed to dehydrate:CREATE TABLE channels");
return NO;
}
NSLog(@"Create table 'channels' successed.");
return YES;
}

【3】向表格中插入一条记录

假设channle是一个数据结构体，保存了一条记录的内容。

- (BOOL) insertOneChannel:(Channel*)channel{
NSData* ImageData = UIImagePNGRepresentation( channel.image_);
NSInteger Imagelen = [ImageData length];
sqlite3_stmt *statement;
static char *sql = "INSERT INTO channels (cid,title,imageData,imageLen)
VALUES(?,?,?)";

//问号的个数要和(cid,imageLen)里面字段的个数匹配，代表未知的值，将在下面将值和字段关联。
int success = sqlite3_prepare_v2(database_,NULL);
if (success != SQLITE_OK) {
NSLog(@"Error: failed to insert:channels");
return NO;
}

//这里的数字1，2，3，4代表第几个问号
sqlite3_bind_text(statement,1,[channel.id_ UTF8String],SQLITE_TRANSIENT);
sqlite3_bind_text(statement,2,[channel.title_ UTF8String],SQLITE_TRANSIENT);
sqlite3_bind_blob(statement,3,[ImageData bytes],Imagelen,SQLITE_TRANSIENT);
sqlite3_bind_int(statement,4,Imagelen);

success = sqlite3_step(statement);
sqlite3_finalize(statement);

if (success == SQLITE_ERROR) {
NSLog(@"Error: failed to insert into the database with message.");
return NO;
}

NSLog(@"Insert One Channel#############:id =%@",channel.id_);
return YES;
}

【4】数据库查询

这里获取表格中所有的记录，放到数组fChannels中。

- (void) getChannels:(NSMutableArray*)fChannels{ sqlite3_stmt *statement = nil; char *sql = "SELECT * FROM channels"; if (sqlite3_prepare_v2(database_,NULL) != SQLITE_OK) { NSLog(@"Error: failed to prepare statement with message:get channels."); } //查询结果集中一条一条的遍历所有的记录，这里的数字对应的是列值。 while (sqlite3_step(statement) == SQLITE_ROW) { char* cid= (char*)sqlite3_column_text(statement,1); char* title= (char*)sqlite3_column_text(statement,2); Byte* imageData = (Byte*)sqlite3_column_blob(statement,3); int imageLen= sqlite3_column_int(statement,4); Channel* channel = [[Channel alloc] init]; if(cid) channel.id_ = [NSString stringWithUTF8String:cid]; if(title) channel.title_ = [NSString stringWithUTF8String:title]; if(imageData){ UIImage* image = [UIImage imageWithData:[NSData dataWithBytes:imageData length:imageLen]]; channel.image_ = image; } [fChannels addObject:channel]; [channel release]; } sqlite3_finalize(statement); }

（编辑：李大同）

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