iphone/iOS開發 – SQLite資料庫使用

iphone開發-SQLite資料庫使用

我現在要使用SQLite3.0建立一個資料庫，然後在資料庫中建立一個表格。

首先要引入SQLite3.0的lib庫。然後包含標頭檔#import <sqlite3.h>【1】 開啟資料庫，如果沒有，那麼建立一個

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];
//找到資料庫檔案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;
        [self createChannelsTable:database_];//在後面實現函數createChannelsTable
        return YES;
    } else {
        sqlite3_close(database_);
        NSLog(@"Error: open database file.");
return NO;
    }
return NO;
}

【2】建立表格

 1 //建立表格，假設有五個欄位，（id，cid，title，imageData ，imageLen ）
 2 //說明一下，id為表格的主鍵，必須有。
 3 //cid，和title都是字串，imageData是位元據，imageLen 是該位元據的長度。
 4 
 5 - (BOOL) createChannelsTable:(sqlite3*)db
 6 {
 7     char *sql = "CREATE TABLE channels (id integer primary key, \
 8                                         cid text, \
 9                                         title text, \
10                                         imageData BLOB, \
11                                         imageLen integer)";
12     sqlite3_stmt *statement;
13     if(sqlite3_prepare_v2(db, sql, -1, &statement, nil) != SQLITE_OK) {
14         NSLog(@"Error: failed to prepare statement:create channels table");
15         return NO;
16     }
17     int success = sqlite3_step(statement);
18     sqlite3_finalize(statement);
19     if ( success != SQLITE_DONE) {
20         NSLog(@"Error: failed to dehydrate:CREATE TABLE channels");
21         return NO;
22     }
23     NSLog(@"Create table 'channels' successed.");
24     return YES;
25 }

 

 【3】 向表格中插入一條記錄假設channle是一個資料結構體，儲存了一條記錄的內容。

- (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(?,?,?,?)";
    //問號的個數要和(cid,title,imageData,imageLen)裡面欄位的個數匹配，代表未知的值，將在下面將值和欄位關聯。
    int success = sqlite3_prepare_v2(database_, sql, -1, &statement, NULL);
if (success != SQLITE_OK) 
    {
        NSLog(@"Error: failed to insert:channels");
return NO;
    }

//這裡的數字1，2，3，4代表第幾個問號
    sqlite3_bind_text(statement, 1, [channel.id_ UTF8String], -1, SQLITE_TRANSIENT);
    sqlite3_bind_text(statement, 2, [channel.title_ UTF8String], -1, 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】資料庫查詢這裡擷取表格中所有的記錄，放到數組fChannels中。

- (void) getChannels:(NSMutableArray*)fChannels
{
    sqlite3_stmt *statement = nil;
char *sql = "SELECT * FROM channels";
if (sqlite3_prepare_v2(database_, sql, -1, &statement, NULL) != SQLITE_OK) 
    {
        NSLog(@"Error: failed to prepare statement with message:get channels.");
    }
//查詢結 果集中一條一條的遍曆所有的記錄，這裡的數字對應的是列值。
    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);
}