Question

所以我想要做的是当我按下按钮时对我的sqlite数据库运行UPDATE查询。下面是我的，它不起作用，我认为问题是我从捆绑打开数据库，这当然是只读的。现在我一直在做一些研究，我意识到我应该：

检查Documents文件夹中是否存在数据库。
如果没有，请将数据库从捆绑包复制到Documents文件夹。
现在，从Documents文件夹中打开数据库。

但我不知道怎么办???任何帮助将不胜感激。这就是我所拥有的：

- (IBAction)update:(id)sender {
@try {
    NSFileManager *fileMgr = [NSFileManager defaultManager];
    NSString *dbPath = [[[NSBundle mainBundle] resourcePath  ]stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"];
    BOOL success = [fileMgr fileExistsAtPath:dbPath];
    if(!success)
    {
        NSLog(@"Cannot locate database file '%@'.", dbPath);
    }
    if(!(sqlite3_open([dbPath UTF8String], &db) == SQLITE_OK))
    {
        NSLog(@"An error has occured: %s", sqlite3_errmsg(db));

    }
    const char *sql = "UPDATE strengthexercises SET isFavorite = 'true' WHERE ID = '1'";
    sqlite3_stmt *sqlStatement;
    if(sqlite3_prepare(db, sql, -1, &sqlStatement, NULL) != SQLITE_OK)
    {
        NSLog(@"Problem with prepare statement:  %s", sqlite3_errmsg(db));
    }else{
        if (sqlite3_step(sqlStatement) == SQLITE_DONE){
            NSLog(@"Success");
        }
    }
    sqlite3_finalize(sqlStatement);
}
@catch (NSException *exception) {
    NSLog(@"Problem with prepare statement:  %s", sqlite3_errmsg(db));
}
@finally {
    sqlite3_close(db);
}

}

有一个例子的明确答案会有很大帮助。提前谢谢。

更新＃1

现在我有了这个，但它仍然不起作用......

- (NSString *)applicationDocumentsDirectory {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
return basePath;
}

 - (IBAction)update:(id)sender {
@try {
    NSString *docsPath = [self applicationDocumentsDirectory];
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"];
    BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:dbPath];
    if (!fileExists) {
        // get the source path to copy from
        NSString *dbSourcePath = [[[NSBundle mainBundle] resourcePath  ]stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"];
        // copy db to documents
        [[NSFileManager defaultManager] copyItemAtPath:dbSourcePath toPath:dbPath error:nil];
    }
    if(!(sqlite3_open([dbPath UTF8String], &db) == SQLITE_OK))
    {
        NSLog(@"An error has occured: %s", sqlite3_errmsg(db));
    }
    const char *sql = "UPDATE strengthexercises SET isFavorite = 'true' WHERE ID = '1'";
    sqlite3_stmt *sqlStatement;
    if(sqlite3_prepare(db, sql, -1, &sqlStatement, NULL) != SQLITE_OK)
    {
        NSLog(@"Problem with prepare statement:  %s", sqlite3_errmsg(db));
    }else{
        if (sqlite3_step(sqlStatement) == SQLITE_DONE){
            NSLog(@"Success");
        }
    }
    sqlite3_finalize(sqlStatement);
}
@catch (NSException *exception) {
    NSLog(@"Problem with prepare statement:  %s", sqlite3_errmsg(db));
}
@finally {
    sqlite3_close(db);
}

}

Answer 1

编写一个方法来返回这样的文档路径 -

- (NSString *)applicationDocumentsDirectory {   
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
     NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
     return basePath;
}

然后检查文档路径中是否存在db -

NSString *docsPath = [self applicationDocumentsDirectory];
NSString *dbDocsPath = [docsPath stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"];
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:dbDocsPath];

使用条件来确定db是否需要复制，如果是，则复制 -

if (!fileExists) {
     // get the source path to copy from
     NSString *dbSourcePath = [[NSBundle mainBundle] pathForResource:@"StayhealthyExercises-1" ofType:@"sqlite"];
     // copy db to documents
     [[NSFileManager defaultManager] copyItemAtPath:dbSourcePath toPath:dbDocsPath error:nil];
}

现在，您应该在可以读/写的文档中拥有数据库的副本。

按下按钮时UPDATE sql查询？

1 个答案: