Hi, I am very new to Julia . Unsurprisingly, I was irritated by the fact that fields are not inherited from a base struct to the other. I clearly know such inheritance is not always desired,. But in some cases, it becomes quite useful, like when writing widgeting system (you dont want to declare posx, posy, width, height, children, onclick, ondragstart, and so on and so forth in every other widget you want)
Hence, I tried writing a macro to do the same. Please let me know if there are any issues. The usage is given later. The usage style could be a bit counterintuitive to some.
Please comment if the following looks good, or if there are any big gotchas. I also think this could be useful to others
theRealType = eval(thetype)
eArray = 
for (thefieldname, thefieldtype) in zip(fieldnames(theRealType), fieldtypes(theRealType))
push!(eArray, Expr(:(::), thefieldname, thefieldtype))
return esc(Expr(:block, eArray...))
How to use this :
geek@geekbox:/home/geek$ julia tryextendingit.jl
A3 <: Any
If you have a lot of common parameters, can’t they be collected in their own type, WidgetParams, which you wrap inside your individual widget types? Seems like repeating fields everywhere may violate DRY.
I’m not at my computer right now, but I think you’ll get an error if two property names are the same. I think if you really, really want inheritance, then the package I linked has already solved this problem. No need to reinvent the wheel.
But in general, @DNF is correct that if you have a common set of parameters, then just make that a struct that can be a field of all widgets. The. You can access fields with mywidget.params.xpos.
That is another way to look at it. I did think about it actually, as a fallback to this macro. But inheritance generally makes the variable names consistent, and it is easy to write multiple dispatch functions this way. Lesser the code, lesser the bugs
Yeah, now that I think of it, Maybe you are right. Will give all different paradigms a try. Only a week since I started learning Julia.
Either way, Just bowled over by how nice, easy and powerful its Meta-programming is. I actually also loved the Julian way of multiple dispatch over regular OOPs . Only thing I hadn’t liked is not being able to share constructors and needing to re enter fields over and over.
But now those seems to be solved … thanks for all the help.
(Need to tell my wife what Julia is. Else will be in trouble if I suddenly scream I Julia)