What is wrong with my join function?

[realapril]

I followed this instruction and I have a problem here

return query.watch().map((rows) {
  return rows.map((row) {
    return EntryWithCategory(
      row.readTable(todos),
      row.readTableOrNull(categories),
    );
  }).toList();
});

problematic lines are these,

row.readTable(todos),
row.readTableOrNull(categories),

the error message says

The argument type '$ToDoTable' can't be assigned to the parameter type 'ResultSetImplementation<$ToDoTable, ToDo>'. 

What have I done wrong? How should I change it?
Acctually my longer code is this one

Stream<List<EntryWithCategory>> entriesWithCategory() =>
  select(todos).join([
    leftOuterJoin(categories, categories.id.equalsExp(todos.category)),
  ])
 .watch()
.map((rows) => rows
 .map((row) => (EntryWithCategory(
      row.readTable(todos),
      row.readTableOrNull(categories),
    ))).toList());

I tried with this one too but it made the same error

Stream<List<EntryWithCategory>> entriesWithCategory() {
    final query = select(todos).join([
      leftOuterJoin(categories, categories.id.equalsExp(todos.category)),
    ]);
    return query.watch().map((rows) {
      return rows.map((row) {
        return EntryWithCategory(
          row.readTable(todos),
          row.readTableOrNull(categories),
        );
      }).toList();
    });
  }

[simolus3]

Could you post the versions of drift and drift_dev that you're using? The generated $ToDoTable should mix in TableInfo which in turn implements ResultSetImplementation.

[realapril]

Drift version is 1.0.1 and drift_dev is 1.0.2, found both in pubsepc.lock file.

[realapril]

Actually both lines are problem so this table is not working too.

The argument type '$CategoryTable' can't be assigned to the parameter type 'ResultSetImplementation<$CategoryTable, Category>

[simolus3]

But if you look at the generated code, $CategoryTable does mixin TableInfo, right? Do you have a small project that reproduces this for me to look at?

[realapril]

While changing some options, my old db is broken.. How can I delete all sqlite3 db and start again? I tried with new emulator too but Unhandled Exception: SqliteException(1): no such table , SQL logic error (code 1) happens over and over.
I tried

• updating schemaVersion
• adding android:allowBackup="false" to manifest
• running app with a new emulator
• delete and reinstall app to the same emulator
• changing .sqlite file's name
  but all were useless.

[simolus3]

If it breaks on a new emulator, it looks like the mistake happens when creating the tables. Can you enable logStatements: true on your NativeDatabase? When you start the app on a new device (or one without a database one it), does it create all the tables?
You can also use NativeDatabase.memory() temporarily to debug issues happening when creating a database.

If not all tables are created, do you have custom code in the onCreate callback of your migration? Otherwise it kind of sounds like a drift problem, but I'll likely need more information to look into it.

[KiritaniAyaka]

TL;DR: You should use generated data class to define the field of your entry class, instead of the class written by yourself

I have the same problem. I made a reproduction and had some try on it.

My conclusion is that Dart gave a wrong error message.

---

There are my classes:

class Person extends Table {
  IntColumn get id => integer().autoIncrement()();
  TextColumn get name => text()();
}

class Post extends Table {
  IntColumn get id => integer().autoIncrement()();
  IntColumn get publisher => integer().references(Person, #id)();
  TextColumn get content => text()();
}

class PostEntry {
  final Person person;
  final Post? posts;
  PostEntry(this.person, this.posts);
}

The same problem occurs while using the code above. The error message is also The argument type '$PersonTable' can't be assigned to the parameter type 'ResultSetImplementation<$PersonTable, Person>'.

As @simolus3 said, I'm exactly determined that $PersonTable mixin-ed TableInfo in generated code, so $PersonTable is compatible with ResultSetImplementation (TableInfo implemented ResultSetImplementation)

But Dart gave an error still, right? I started trying to dig with it:

Let's see the signature of the readTable method:

D readTable<T extends HasResultSet, D>(ResultSetImplementation<T, D> table)

tableInfo:

mixin TableInfo<TableDsl extends Table, D> on Table
    implements DatabaseSchemaEntity, ResultSetImplementation<TableDsl, D>

and generated class $PersonTable:

class $PersonTable extends Person with TableInfo<$PersonTable, PersonData>

Pay attention to the generic type D, we can infer that readTable returns a PersonData.

But our PostEntry constructor is:

class PostEntry {
  final Person person;
  final Post posts;
  PostEntry(this.person, this.posts);
}

Yep, the correct error message should be The argument type 'PersonData' can't be assigned to the parameter type 'Person'.

Changing our PostEntry to look like this:

class PostEntry {
  final PersonData person;
  final PostData? posts;
  PostEntry(this.person, this.posts);
}

The error was dismissed "magically".

---

If anybody wants to further dig with the bug of Dart, I could upload the whole project later and there are dependencies I used:

dependencies:
  drift: ^2.6.0
  sqlite3_flutter_libs: ^0.5.13
  path_provider: ^2.0.14
dev_dependencies:
  flutter_lints: ^2.0.0
  drift_dev: ^2.6.0
  build_runner: ^2.3.3

$ flutter --version
Flutter 3.7.9 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 62bd79521d (4 days ago) • 2023-03-30 10:59:36 -0700
Engine • revision ec975089ac
Tools • Dart 2.19.6 • DevTools 2.20.1

[mccoyg]

@simolus3 Hi, would you please mind updating the docs: https://drift.simonbinder.eu/docs/dart-api/select/#joins -

1. update and cap off the joins sections with an actual return for normal (two table joins) instead of "// see next section on how to parse the result" and then never resolve it because in "Parse Results" you resolve the 2+ multiple table example.
2. Please Incorporate @KiritaniAyaka to describe how to create the data class using the generated "D" datatypes.

Even if you ignore these suggestions, Thank you!

[simolus3]

and then never resolve it because in "Parse Results" you resolve the 2+ multiple table example.

It's actually the same example, but that's a good point - I'll change the snippet to be more complete. I've also added a comment to the EntryWithCategory class from the example to explicitly mention that the two fields are using the classes generated by drift instead of the source table classes.