WriteVTK: MeshCell not a concrete type

[fredrikekre]

For VTK export we allocate the vector of output like this

Ferrite.jl/src/Export/VTK.jl

Line 118 in 3b081be

cls = WriteVTK.MeshCell[]

which, when this code was written, was a concrete type. Since JuliaVTK/WriteVTK.jl@1850714 this isn't the case anymore, and the MeshCell type have changed a couple of times after this commit too. Current definition: https://github.com/JuliaVTK/VTKBase.jl/blob/1f48d195fdf5bf35254228cca4797452c7b94d3d/src/mesh_cells.jl#L55-L66

It looks like it can now stored the node id tuple directly too, meaning we can remove the allocation of a small vector for each cell by removing the call to collect here:

Ferrite.jl/src/Export/VTK.jl

Line 85 in 3b081be

nodes_to_vtkorder(cell::AbstractCell) = collect(cell.nodes)

xref: JuliaVTK/WriteVTK.jl#156