`size` has no method matching size(::Data{Float32}) when using nested composite type in julia -

say defined composite type "data" follows:

type dataformat     format1::datatype     format2::uint     format3::uint     format4::ptr{none} end  type data{t} <: abstractvector{t}     value::vector{t}     format::dataformat     end 

it's ok when run myformat = dataformat(float32, 0, 0, c_null). run mydata = data{float32}([0.1, 0.2, 0.3], myformat), these errors appear:

error showing value of type data{float32}: error: `size` has no method matching size(::data{float32}) in writemime @ replutil.jl:18 in display @ repl.jl:117 in display @ repl.jl:120 in display @ multimedia.jl:149 in print_response @ repl.jl:139 in print_response @ repl.jl:124 in anonymous @ repl.jl:586 in run_interface @ /opt/homebrew-cask/caskroom/julia/0.3.7/julia-      0.3.7.app/contents/resources/julia/lib/julia/sys.dylib in run_frontend @ /opt/homebrew-cask/caskroom/julia/0.3.7/julia-0.3.7.app/contents/resources/julia/lib/julia/sys.dylib in run_repl @ /opt/homebrew-cask/caskroom/julia/0.3.7/julia-0.3.7.app/contents/resources/julia/lib/julia/sys.dylib in _start @ /opt/homebrew-cask/caskroom/julia/0.3.7/julia-0.3.7.app/contents/resources/julia/lib/julia/sys.dylib 

it seems broken julia's size() function, how can fix it? i'm new julia , don't know whether it's choice use "nested" composite type this?

it's relatively straightforward extend size:

julia> import base.size  julia> size(d::data) = size(d.value) size (generic function 51 methods) 

if want datatype support other operations iteration , indexing you'll need define getindex, start, next, length , done

edit: see comment below why start, next, length , done not necessary.