NSArray 在 for 循环中使用时使我的程序崩溃

Question

我正在使用 SQLite3 从数据库中获取数据。所以我试图制作一个多维数组来保存所有记录的数组，这是一个数组中的嵌套数组。所以当循环到达这段代码时：

[[studentsInfo objectAtIndex:recordRow] addObject: [NSMutableArray arrayWithObjects:studentLastName, studentFirstName, studentID, studentEmail, programName, majorityCampus, discipline, cmName, cmID, cmEmail, cmPhone, cmCampus, studentNotes, nil]];

它崩溃了。这是我从 Xcode.

得到的

这是完整代码我做错了什么？

    - (void) initializeDatabase {

    // get the documents directory
    NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docsDir = dirPaths[0];
    NSLog(@"Directory Path: %@", docsDir);

    FindYourMentorDB_Path = [[NSString alloc]initWithString:[docsDir stringByAppendingPathComponent:@"FindYourCM_Info.sqlite"]];

    NSFileManager *fileManager = [NSFileManager defaultManager];

    if ([fileManager fileExistsAtPath:FindYourMentorDB_Path] == NO) {

        // attempt to open the db
        if (sqlite3_open([FindYourMentorDB_Path UTF8String], &_FindYourMentorDB) == SQLITE_OK){

            sqlite3_close(_FindYourMentorDB); // Close the DB

            NSLog(@"Succeeded in opening FindYourMentorDB");
        } else {

            NSLog(@"Failed to Open the FindYourMentorDB");
        } // END OF IF

    } // END OF IF

    NSMutableArray *studentsInfo = [NSMutableArray new];

    sqlite3_stmt *statement;

    if (sqlite3_open([FindYourMentorDB_Path UTF8String], &_FindYourMentorDB) == SQLITE_OK) {

        NSString *selectSQL = [NSString stringWithFormat:@"SELECT StudentLastName, StudentFirstName, StudentID, StudentEmail, ProgramName, MajorityCampus, Discipline, CMName, CMID, CMEmail, CMPhone, CMCampus, StudentNotes FROM FindYourCM_DB"];

        const char *selectStmt = [selectSQL UTF8String];

        if (sqlite3_prepare_v2(_FindYourMentorDB, selectStmt, -1, &statement, NULL) == SQLITE_OK) {

            for (int recordRow = 0; sqlite3_step(statement) == SQLITE_ROW; recordRow++) {

                NSString *studentLastName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement,0)];

                NSString *studentFirstName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 1)];

                NSString *studentID = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 2)];

                NSString *studentEmail = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 3)];

                NSString *programName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 4)];

                NSString *majorityCampus = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 5)];

                NSString *discipline = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 6)];

                NSString *cmName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 7)];

                NSString *cmID = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 8)];

                NSString *cmEmail = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 9)];

                NSString *cmPhone = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 10)];

                NSString *cmCampus = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 11)];

                NSString *studentNotes = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 12)];

                [[studentsInfo objectAtIndex:recordRow] addObject: [NSMutableArray arrayWithObjects:studentLastName, studentFirstName, studentID, studentEmail, programName, majorityCampus, discipline, cmName, cmID, cmEmail, cmPhone, cmCampus, studentNotes, nil]];
            }

            sqlite3_finalize(statement);
        }

        sqlite3_close(_FindYourMentorDB);
    }
}

Answer 1

主要问题是这一行：

[[studentsInfo objectAtIndex:recordRow] addObject: [NSMutableArray arrayWithObjects:studentLastName, studentFirstName, ...

由于 studentsInfo 是一个新的空数组，因此无法从中访问任何内容。您只需按如下方式添加到其中：

[studentsInfo addObject: [NSMutableArray arrayWithObjects:studentLastName, studentFirstName, ...

您还可以清理其他一些东西。

- (void) initializeDatabase {
    // get the documents directory
    NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docsDir = dirPaths[0];
    NSLog(@"Directory Path: %@", docsDir);

    findYourMentorDB_Path = [docsDir stringByAppendingPathComponent:@"FindYourCM_Info.sqlite"];

    NSMutableArray *studentsInfo = [NSMutableArray new];

    if (sqlite3_open([findYourMentorDB_Path UTF8String], &_findYourMentorDB) == SQLITE_OK) {
        NSString *selectSQL = @"SELECT StudentLastName, StudentFirstName, StudentID, StudentEmail, ProgramName, MajorityCampus, Discipline, CMName, CMID, CMEmail, CMPhone, CMCampus, StudentNotes FROM FindYourCM_DB";

        const char *selectStmt = [selectSQL UTF8String];

        sqlite3_stmt *statement;
        if (sqlite3_prepare_v2(_findYourMentorDB, selectStmt, -1, &statement, NULL) == SQLITE_OK) {
            while (sqlite3_step(statement) == SQLITE_ROW) {
                NSString *studentLastName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement,0)];
                NSString *studentFirstName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 1)];
                NSString *studentID = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 2)];
                NSString *studentEmail = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 3)];
                NSString *programName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 4)];
                NSString *majorityCampus = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 5)];
                NSString *discipline = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 6)];
                NSString *cmName = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 7)];
                NSString *cmID = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 8)];
                NSString *cmEmail = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 9)];
                NSString *cmPhone = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 10)];
                NSString *cmCampus = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 11)];
                NSString *studentNotes = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 12)];

                [studentsInfo addObject:@[ studentLastName, studentFirstName, studentID, studentEmail, programName, majorityCampus, discipline, cmName, cmID, cmEmail, cmPhone, cmCampus, studentNotes ]];
            }

            sqlite3_finalize(statement);
        } else {
            NSLog(@"Unable to prepare statement: %s", sqlite3_errmsg(_findYourMentorDB));
        }

        sqlite3_close(_findYourMentorDB);
    } else {
        NSLog(@"Unable to open database at %@", findYourMentorDB_Path);
    }
}

问题：

填充 studentsInfo 数组后如何处理它？
使用正确的命名约定 - 变量和方法名称应以小写字母开头。 Class 名称以大写字母开头。
记录错误，以便您了解为什么无法正常工作。
您对数据库文件的检查后跟一个不必要的打开和关闭是不需要的。如果数据库文件不存在，使用sqlite3_open.

Answer 2

我明白了。数据库中的 StudentNotes 为 NULL，因此导致它崩溃。所以我把代码改成了这个。感谢大家的帮助。

Answer 3

使用了下一个方法：insertObject:yourarray atIndex:yourindex

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