I read in a book that "you can't create traditional 'classes' in julia with single-dispatch-style methods like obj.myfunc()
" ... and I thought that sounded more like a challenge than a fact.
So here's my JavaClass
type with public / private fields and methods just for the sheer shock and horror factor of having something ugly like this in Julia, after all the trouble the devs have gone to to avoid it:
type JavaClass
# Public fields
name::String
# Public methods
getName::Function
setName::Function
getX::Function
getY::Function
setX::Function
setY::Function
# Primary Constructor - "through Whom all things were made."
function JavaClass(namearg::String, xarg::Int64, yarg::Int64)
# Private fields - implemented as "closed" variables
x = xarg
y = yarg
# Private methods used for "overloading"
setY(yarg::Int64) = (y = yarg; return nothing)
setY(yarg::Float64) = (y = Int64(yarg * 1000); return nothing)
# Construct object
this = new()
this.name = namearg
this.getName = () -> this.name
this.setName = (name::String) -> (this.name = name; return nothing)
this.getX = () -> x
this.getY = () -> y
this.setX = (xarg::Int64) -> (x = xarg; return nothing)
this.setY = (yarg) -> setY(yarg) #Select appropriate overloaded method
# Return constructed object
return this
end
# a secondary (inner) constructor
JavaClass(namearg::String) = JavaClass(namearg, 0,0)
end
Example use:
julia> a = JavaClass("John", 10, 20);
julia> a.name # public
"John"
julia> a.name = "Jim";
julia> a.getName()
"Jim"
julia> a.setName("Jack")
julia> a.getName()
"Jack"
julia> a.x # private, cannot access
ERROR: type JavaClass has no field x
julia> a.getX()
10
julia> a.setX(11)
julia> a.getX()
11
julia> a.setY(2) # "single-dispatch" call to Int overloaded method
julia> a.getY()
2
julia> a.setY(2.0)
julia> a.getY() # "single-dispatch" call to Float overloaded method
2000
julia> b = JavaClass("Jill"); # secondary constructor
julia> b.getX()
0
Essentially, the constructor becomes a closure, which is how one creates "private" fields and methods / overloading.
Any thoughts? (other than "OMG Why??? Why would you do this??")
Any other approaches?
Any scenarios you could envisage where this might fail spectacularly?