我在一本书中读到过这样一句话:“你无法使用单派发方式的方法(例如 obj.myfunc()
)在julia中创建传统的'类'”...但我认为这听起来更像是挑战而不是事实。
因此,这里是我的 JavaClass
类型,拥有公共/私有字段和方法,仅为了纯粹的震惊和恐怖因素,就像在Julia中有这样丑陋的东西一样,尽管开发人员们已经尽力避免它:
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
使用示例:
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
本质上,构造函数成为了一个闭包,这就是如何创建“私有”字段和方法/重载的方式。
除了“天啊,为什么??为什么要这么做?”之外,还有什么想法吗?
还有其他方法吗?
您能想象会出现哪些可能会惨败的情况吗?