Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
Not necessarily the global scope, more like scope within a for statement, or a proc
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
You can't exit the global scope except by exiting the program because its scope is the program.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
Hmm? Destructors aren’t automatically called when the scope is left? Why is that? I’ve been looking into this for the past 3-4 days (since I started trying to port some simple Python scripts to Nim) with no luck, only to find this.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
Oh I see; I had assumed your container API was generic (in the sense of parametric polymorphism) but you have some kind of subtyping there. I hope that when Nim 1.0 comes in 2037 that there's a different solution than the current `method`. Something more minimalistic, like Ada (>95) provides. I think those would address your use case.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
Maybe we should also mention that all object variants of a collection have the same size (occupied bytes in ram). For very heterogeneous objects like graphical elements (plain line vs complicated element) that may wast some memory.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
Library users cannot change the `kind` discriminant of an object variant without forking the library. For example in Arraymancer, if you have some neural network layers predefined from super simple (addition, matrix multiplication, mean, sum) to more complex (convolutions, softmax, ...). I can't hardcode the `kind` of layers as that would prevent users to define their own without forking the "LayerKind" enum.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
> For a library, when you need to build a heterogeneous collection of objects > with types that can be user defined. Why don't object variants work here, instead of OOP? I don't see the need to introduce method for this case. The only thing OO provides is open recursion, which I haven't needed in most of the code I write.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
My opinion is that OOP in Nim is necessary in a very specific case: * For a library, when you need to build a heterogeneous collection of objects with types that can be user defined. Anywhere else I actively try to avoid it. And for naive getter and setter, you can just make the fields public. They are useful only if input must be validated or update is not trivial (like for the times module).
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
The most weird OOP syntax . Thats what is Nim OOP.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
They are called. But sometimes unexpectedly. For assignment of an object to a gloabal variable destructor currently is called just after assignment (if not changed already).
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
proc `=destroy`(self: var SomeClass) = echo "destroying " & $self Run Destructors work not very smoothly. At least with global variables. Types (including object types) are infered in Nim. As `newSomeClass` is declared above as returning `SomeClass`, you don't need to declare the variable's type - compiler can determine it unambiguously. But you still can to state it explicitly, `var Aclass: SomeClass = ...`, compiler will check it. You can assign variable later, then its type is required at definition. I.e., this all is not related to OOP, just to variables. Very concise still exhaustive Nim's [manual](https://nim-lang.org/docs/manual.html) explains well both topics.
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
Just write it like any other `proc`, although currently it is not possible for them to be automatically triggered when a variable gone out of scope: type SomeClass* = object m_Var1: int m_Str1: string m_For_Prop: int proc destroySomeClass*(sc: var SomeClass) = sc.m_Var1 = 0 sc.m_Str1 = "" Run
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
@LeuGim, Thanks for the reply. Now everything is clear to me. Great explanation. But one thing i forgot to add in my VB.Net class. How write a destructor proc in Nim ?
Re: Confused with Nim OOP tutorials. Please clarify straight forward examples
E.g. so: # module1.nim type SomeClass* = object m_Var1: int m_Str1: string m_For_Prop: int proc newSomeClass*: SomeClass = result.m_Var1 = 5400 result.m_Str1 = "A String from consrtuctor" proc PrintMembes*(self: SomeClass) = echo self.m_Var1 echo self.m_Str1 echo self.m_For_Prop proc AProp*(self: SomeClass): int = self.m_For_prop proc `AProp=`*(self: var SomeClass, value: int) = self.m_For_Prop = value # module2.nim import module1 var Aclass = newSomeClass() Aclass.PrintMembes Aclass.AProp = 555 Run * `self` is just a parameter name, you can use `this`, `obj` or whatever you want instead * `*` is to make public: that is you can access these symbols in other modules * the set of procedures working on a type is not fixed, you can add such "methods of SomeClass" in other modules; and you can call them like `PrintMembes(Aclass)` too; they are just procedures
Confused with Nim OOP tutorials. Please clarify straight forward examples
Hi, i cant digest the example in OOP section. This is a class example is from VB.Net. Please somebody translate this into Nim, so that i can easily understand what Nim offers. 1. Public Class SomeClass 2. Private m_Var1 As Integer '// An Integer member variable 3. Private m_Str1 As String '// A String memeber var 4. Private m_For_Prop As Integer '// An integer for property 5. Public Sub New() '// A constructor without any params 6. Me.m_Var1 = 5400 '// initialized member var with value 5400 7. Me.m_Str1 = "A String from constructor" '// Initialized member string 8. End Sub 9. 1. Public Sub PrintMembes() '// A method to print the member values 2. Console.WriteLine(Me.m_Var1) 3. Console.WriteLine(Me.m_Str1) 4. End Sub 5. Public Property AProp() As Integer '// A public property which we can read and write 6. Get 7. Return Me.m_For_Prop 8. End Get 9. Set(ByVal Value As Integer) 10. Me.m_For_Prop= value 11. End Set 12. End Property 13. End Class
