FlatBuffers - Error when creating Vector of struct

Question

I am very new to flatbuffers and believe I am following the tutorial correctly but modifying it to my needs, but cannot for the life of me work out why i'm getting this error:

 error: could not convert ‘_Positions’ from ‘flatbuffers::Offset<flatbuffers::Vector<Renderer::Import::Vec3> >’ to ‘flatbuffers::Offset<flatbuffers::Vector<const Renderer::Import::Vec3*> >’
                                        _Materials, _Faces);

in addition, I've just noticed it's also throwing error: static assertion failed: T must be a scalar type thrice

Flatbuffers Schema:

namespace Renderer.Import;
struct Vec3 {
...
}


struct Face {
...
}
struct Material{
...
}

table Mesh{
  Name:string;
  Positions:[Vec3];
  Normals:[Vec3];
  Materials:[Material];
  Faces:[Face];
}

C++ Code:

  flatbuffers::FlatBufferBuilder builder(4096);

  std::vector<Renderer::Import::Vec3> Normals;
  // Populate

  std::vector<Renderer::Import::Vec3> Positions;
  // Populate

  std::vector<Renderer::Import::Material> Materials;
  // Populate

 std::vector<Renderer::Import::Face> Faces;
 // Populate

    auto _Name = builder.CreateString(shapes[0].name);
    auto _Normals = builder.CreateVector(Normals);
    auto _Positions = builder.CreateVector(Positions);
    auto _Materials = builder.CreateVector(Materials);
    auto _Faces = builder.CreateVector(Faces);
    // Errors with `_Position` argument, but maybe the other three are incorrect too
    auto mesh = Renderer::Import::CreateMesh(builder, _Name, _Positions, _Normals, _Materials, _Faces);

Any help on this issue would be greatly appreciated

Notice that the error you pasted filtered out some characters, so it is hard to say what the problem is.. can you re-paste as a code block? your schema and code look otherwise correct to me. Both `_Positions` and the 3rd arg to `CreateMesh` should be the same type. — Aardappel, Feb 26 '17 at 17:45
Were you in debug mode (assertions on) when you tried this? Because when I try passing a vector of structs to `CreateVector`, I get `error: static assertion failed: T must be a scalar type`. — Aardappel, May 11 '17 at 00:58

score 3 · Accepted Answer · answered Feb 26 '17 at 20:55

3

Use CreateVectorOfStructs instead of CreateVector when used with structs.

The API is to blame for accepting a vector of structs with CreateVector, we'll have to fix that.

answered Feb 26 '17 at 20:55

Aardappel

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It should give: `error: static assertion failed: T must be a scalar type` – Aardappel May 11 '17 at 00:59
Doesn't this then mean you would not be able to use the auto-generated `Mesh` class to read your `Mesh` tables because it is expecting the results of `CreateVector` and not the results of `CreateVectorOfStructs`? – mcmcc Jan 31 '18 at 19:53
@mcmcc Where does it expect the result of CreateVector? Note that this commit may have fixed some of this: https://github.com/google/flatbuffers/commit/fee9afd80b6358a63b92b6991d858604da524e2b If not, please file an issue on github – Aardappel Jan 31 '18 at 23:48
I'm somewhat new to flatbuffers and I was confused about the (inoperability) consequences of choosing `CreateVectorOfStructs` vs `CreateVector`. Now I think it was a misunderstanding on my part. And yes, it looks like that fix might relieve a lot of confusion and simplify a lot of code. Any idea of when that will appear in a tagged release? – mcmcc Feb 02 '18 at 04:50
I have no idea when the next tagged release will be... I can look into it. – Aardappel Feb 02 '18 at 15:13

FlatBuffers - Error when creating Vector of struct

1 Answers1