try to draw vector of Mesh => ggez::graphics::mesh::Mesh is private module

[laticoda]

I dont know how to work with a vector of meshes to draw it

i got this error
let mut vec_of_mesh: Vecggez::graphics::mesh::Mesh = Vec::new();
| ^^^^ private module

vec_of_mesh.push(mb.line(foo_A, foo_B, foo_C).unwrap());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct ggez::graphics::mesh::Mesh, found &mut ggez::graphics::mesh::MeshBuilder

my code

struct MainState {   
    meshes: Vec<ggez::graphics::Mesh>,
}

impl EventHandler for MainState {
fn draw(&mut self, ctx: &mut ggez::Context) -> ggez::GameResult {
        
        graphics::clear(ctx, Color::new(0.0, 0.0, 0.0, 1.0));

        let mb = &mut graphics::MeshBuilder::new();        

        let foo_A = &[
                Point2::new(200.0, 200.0),
                Point2::new(400.0, 200.0),
                Point2::new(400.0, 400.0),
                Point2::new(200.0, 400.0),
                Point2::new(200.0, 300.0),
            ];

        let foo_B = 4.0;
        let foo_C = Color::new(1.0, 0.0, 0.0, 1.0);
        let mut vec_of_mesh: Vec<ggez::graphics::mesh::Mesh> = Vec::new();
        vec_of_mesh.push(mb.line(foo_A, foo_B, foo_C).unwrap());
        for m in &vec_of_mesh {
            graphics::draw(ctx, m, graphics::DrawParam::new())?;
        }
        graphics::present(ctx).expect("error presenting");
        Ok(())
    }

[BrettWitty]

Did you forget to run build(ctx) to create the mesh?

In particular I think the line with the error needs to be:
vec_of_mesh.push(mb.line(foo_A, foo_B, foo_C).build(ctx).unwrap());

[laticoda]

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=5dd2db33cf493c4efe410688b8273b73

line 53 private method
line 56
**method not found in std::result::Result<&mut ggez::graphics::mesh::MeshBuilder, ggez::error::GameError>
**

[Manghi]

There are two issues I see:

1. The mesh module is purposefully private so that users of this library can't access it; it is only public if accessed within the ggez crate. That is why it's marked pub(crate) in mod.rs (see here). But the developers know that you need to access the goodies within so they still let you do so without going into the mesh module. All of the goodies are made public because of line 58 pub use crate::graphics::mesh::*; (see here). This enables you to access the Mesh data structure by going through the graphics module.

2. mb.line(foo_A, foo_B, foo_C) returns a Result<MeshBuilder, GameError>, so you need to handle the Result first before you can call build(ctx) on it. The try operator ? is some syntactic sugar to help you with this. It would be easier to see the flow of things if you split line 56 in your example into three lines for clarity.

All together:

let mut vec_of_mesh: Vec<graphics::Mesh> = Vec::new(); // use graphics::Mesh and not graphics::mesh::Mesh

let mb = mb.line(foo_A, foo_B, foo_C)?; // Handle the result first using '?'
let built_mesh = mb.build(ctx)?;        // Then build the mesh (and yet again handle the result)
vec_of_mesh.push(built_mesh);           // Finally store it in your vector

Hope this helps.

One other small thing. You have both

use ggez::graphics;
...
use ggez::graphics::{Color, DrawMode};

but you can shorten this to

use ggez::graphics::{self, Color, DrawMode};

I would recommend referring to these resources if you want to learn more:
https://doc.rust-lang.org/reference/visibility-and-privacy.html
https://doc.rust-lang.org/edition-guide/rust-2018/error-handling-and-panics/the-question-mark-operator-for-easier-error-handling.html

[laticoda]

thank you everybody