Re: [julia-users] Extending a DataFrame (or, why aren't my imports working?)

[kevin . dale . smith]

Ok, I narrowed it down to a very small test case.  The mymodule.jl file is 
at the bottom of this posting.  If you save that to a file then run this 
code, you'll get the same effect as my original problem except with the 
'index' method.

using mymodule

mydf = MyDataFrame(Any[], Index())

# This line complains that `index` has no method matching 
index(::MyDataFrame)
display(mydf)

# This displays my `index` method
methods(index)

# This shows that my `index` method works
index(mydf)
 

=== mymodule.jl ===

module mymodule

import DataFrames: AbstractDataFrame, DataFrame, Index, nrow, ncol
import DataArrays: DataArray

export MyDataFrame, nrow, ncol, Index, index, columns

type MyDataFrame <: AbstractDataFrame
   columns::Vector{Any}
   colindex::Index

   function MyDataFrame(columns::Vector{Any}, colindex::Index)

      ncols = length(columns)
      if ncols > 1
          nrows = length(columns[1])
          equallengths = true
          for i in 2:ncols
              equallengths &= length(columns[i]) == nrows
          end
          if !equallengths
              msg = "All columns in a DataFrame must be the same length"
              throw(ArgumentError(msg))
          end
      end

      if length(colindex) != ncols
          msg = "Columns and column index must be the same length"
          throw(ArgumentError(msg))
      end

      new(columns, colindex)
   end

end

index(df::MyDataFrame) = df.colindex
columns(df::MyDataFrame) = df.columns

nrow(df::MyDataFrame) = ncol(df) > 0 ? length(df.columns[1])::Int : 0
ncol(df::MyDataFrame) = length(index(df))

end

==================