Question

我的iPhone项目中有以下功能，效果很好......除非查询没有返回任何内容然后应用程序崩溃。调试很麻烦，根本没有激活任何断点！

我知道这是有效的，因为我传入了DB中的静态内容并返回一个值。

-(NSString *)getSomeText:(NSString *)toPass {
    sqlite3 *database;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *databasePath = [documentsDirectory stringByAppendingPathComponent:@"sf.sqlite"];

    int strLength = 0;
    strLength = [toPass length];

    if (strLength <3)
        return @"Unknown";


    NSString *MIDstr;
    NSMutableString * toPass Copy = [NSMutableString stringWithString:toPass];
    MIDstr = [toPassCopy substringWithRange:NSMakeRange(0, 3)];


    // Open the database from the users filessytem
    if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) {
        // Setup the SQL Statement and compile it for faster access
        NSString *BaseSQL = [NSString stringWithFormat:@"select * from MIDS where MID = '%@'",MIDstr];
        NSLog(BaseSQL);

        const char *sqlStatement = [BaseSQL UTF8String];
        //NSLog(BaseSQL);
        sqlite3_stmt *compiledStatement;
        if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) {
            // Loop through the results and add them to the feeds array

            while(sqlite3_step(compiledStatement) == SQLITE_ROW) {


                    NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];
                    NSString *returnString = [NSString stringWithFormat:@"%@",aName];
                    return returnString;                

            }
        }
        // Release the compiled statement from memory
        sqlite3_finalize(compiledStatement);

    }
    sqlite3_close(database);

}

Answer 1

一个。如果 sqlite3_step 没有返回任何行，则会因为声明要返回NSString而崩溃，但是如果没有行则不返回任何行。调用者将尝试从堆栈中读取NSString，从而最终取消引用垃圾。

要快速解决问题，请写下：

    sqlite3_close(database);
    return nil;
}

并确保调用者处理 nil 结果。

B /如果您执行拥有数据，您的代码永远不会调用 sqlite3_finalize 和 sqlite3_close ，因为您提前返回：

while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
    [..]
    return returnString;

Answer 2

while (sqlite3_step(sqlstatement) == SQLITE_ROW )
            {
                //Your code goes here

            }

            sqlite3_finalize(sqlstatement);
            sqlite3_close(databaseRefObj);

关闭数据库并在while循环后完成你的语句，这帮助了我，

如果没有返回行，iphone sqlite查询崩溃

2 个答案: