On Sep 21, 2016 9:42 AM, "Randy Zwitch" <randy.zwi...@fuqua.duke.edu> wrote:
>
> I frequently have a design pattern of Union{Title, Void}. I was thinking
that I could redefine this as title::Nullable{Title}. However, once I try
to modify fields inside the Title type using setfield!(ec.title, k, v), I
get this error message:
>
> LoadError: type Nullable is immutable while loading In[19], in expression
starting on line 4
>
>
>
> My question is, why is the Nullable type immutable? My original thought
was that my Nullable definition was saying "There is either a Title type
here or nothing/missing", and maybe I know the value now or maybe I know it
later. But it seems the definition is actually "There could be a Title type
here or missing, and whatever you see first is what you will always have"
>
> Is there a better way to express the former behavior other than as a
Union type? My use case is building JSON strings as specifications of
graphs for JavaScript libraries, so nearly every field of every type is
possibly missing for any given specification.
Assign the whole object instead of mutating it.
>
> @with_kw type EChart <: AbstractEChartType
> # title::Union{Title,Void} = Title()
> title::Nullable{Title} = Title()
> legend::Union{Legend,Void} = nothing
> grid::Union{Grid,Void} = nothing
> xAxis::Union{Array{Axis,1},Void} = nothing
> yAxis::Union{Array{Axis,1},Void} = nothing
> polar::Union{Polar,Void} = nothing
> radiusAxis::Union{RadiusAxis,Void} = nothing
> angleAxis::Union{AngleAxis,Void} = nothing
> radar::Union{Radar,Void} = nothing
> dataZoom::Union{DataZoom,Void} = nothing
> visualMap::Union{VisualMap,Void} = nothing
> tooltip::Union{Tooltip,Void} = nothing
> toolbox::Union{Toolbox,Void} = Toolbox()
> geo::Union{Geo,Void} = nothing
> parallel::Union{Parallel,Void} = nothing
> parallelAxis::Union{ParallelAxis,Void} = nothing
> timeline::Union{Timeline,Void} = nothing
> series::Union{Array{Series,1},Void} = nothing
> color::Union{AbstractVector,Void} = nothing
> backgroundColor::Union{String,Void} = nothing
> textStyle::Union{TextStyle,Void} = nothing
> animation::Union{Bool,Void} = nothing
> animationDuration::Union{Int,Void} = nothing
> animationEasing::Union{String,Void} = nothing
> animationDelay::Union{Int,Void} = nothing
> animationDurationUpdate::Union{Int,Void} = nothing
> animationEasingUpdate::Union{String,Void} = nothing
> animationDelayUpdate::Union{Int,Void} = nothing
> end
