Missing / Out-of-Order Code in Tutorial

The Issue

Throughout the Bevy engine chess tutorial there are a number of places where the program will not function as described by the tutorial because code required for error-free execution (i.e. variable declarations) was not introduced at the step it should have been.

Specifics

Cannot find type `Piece` in this scope.

In the tutorial after the paragraph: "We now need to implement something to change the unit positions. We'll change the select_square system to also move the pieces for now, and we'll refactor it into something neater later:" the following code is displayed:

fn select_square(
    pick_state: Res<PickState>,
    mouse_button_inputs: Res<Input<MouseButton>>,
    mut selected_square: ResMut<SelectedSquare>,
    mut selected_piece: ResMut<SelectedPiece>,
    squares_query: Query<&Square>,
    mut pieces_query: Query<(Entity, &mut Piece)>,
) {

At this point, you will receive the error "Cannot find type Piece in this scope.".

Solution: change the PieceColor, PieceType, and Piece structs to all be public and add use crate::pieces::* to the top of board.rs. The tutorial shows neither of these steps, but the final code does.

Cannot find value `pieces_vec` in this scope.

In the tutorial after the paragraph: "Finally, we just need to call the function before moving a piece to check that the move is valid:" the following code is displayed:

fn select_square(
                [...]

                // Move the selected piece to the selected square
                if let Ok((_piece_entity, mut piece)) = pieces_query.get_mut(selected_piece_entity)
                {
                    if piece.is_move_valid((square.x, square.y), pieces_vec) {
                        piece.x = square.x;
                        piece.y = square.y;
                    }
                }

                [...]
}

At this point, you will receive the error "Cannot find value pieces_vec in this scope.".

Solution: add let pieces_vec = pieces_query.iter_mut().map(|(_, piece)| *piece).collect(); under the line if let Ok((_piece_entity, mut piece)) = pieces_query.get_mut(selected_piece_entity).

Note: The tuple inside the .map(| |) closure and Ok(()) lines only contains two arguments as the children argument has not been introduced by this point in the tutorial.

Field `0` of struct `bevy::prelude::Children` is private

In the tutorial after the paragraph: "Here's the new function that also takes care of despawning a piece after it's taken:" the following code is displayed:

...
 let pieces_entity_vec: Vec<(Entity, Piece, Vec<Entity>)> = pieces_query
                    .iter_mut()
                    .map(|(entity, piece, children)| {
                        (
                            entity,
                            *piece,
                            children.0.iter().map(|entity| *entity).collect(),
                        )
                    })
                    .collect();
...

At this point, you will receive the error "field 0 of struct bevy::prelude::Children is private" on the children.0.iter()... line.

Solution: Change children.0.iter() to children.iter(). This solution I don't understand as much since I just got it from tubotinatub on the Discord.

That is all. Let me know if I was mistaken or if you need help understanding any of these issues.

Thanks again for the great tutorial. It's really helped me grasp Bevy.

guimcaballero / bevy_chess