按下按钮时更新sql查询？

Question

所以我想要做的是在我按下按钮时对我的 sqlite 数据库运行 UPDATE 查询。下面是我所拥有的但它不起作用，我认为问题是我正在从包中打开数据库，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：

1. 检查 Documents 文件夹中是否存在数据库。

2. 如果不存在，请将数据库从捆绑包复制到 Documents 文件夹。

3. 现在，从 Documents 文件夹打开数据库。

但我不知道该怎么做？？？任何帮助将不胜感激。这是我所拥有的：

- (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);
}

}

用一个例子给出一个明确的答案会很有帮助。提前致谢。

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

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，如果需要，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];
}

您现在应该在可以读取/写入的文档中拥有您的数据库副本。