More questions

einhugur

Sorry that I am spamming you with questions.

Question1:

How to make a constructor on a class ?

The above fails.

Question 2

How to construct instance of a class from TypeInfo ? So when p is of type Person bellow,

Then ideally I would want to be able to construct more Persons but without knowing anything about the class as in construct it through introspection from the TypeInfo.

Var ti As TypeInfo = typeof(p)

Garry

No need to apologise, this is all excellent feedback so thank you.

Constructors are declared with the Constructor keyword internally. They are not normal Subs named Constructor.

In Studio, use Add > Constructor on the class, rather than adding a method and naming it Constructor.

For your second question, yes, this is what TypeInfo.CreateInstance() is for:

Var p As New Person("Alice")
Var ti As TypeInfo = TypeOf(p)

Var p2 As Object = ti.CreateInstance("Bob")
Print(GetProperty(p2, "Name")) # Bob

So this is partly a Studio UI bug: Studio should not let a normal method be renamed to Constructor, because Constructor is a keyword and produces invalid ObjoBasic. I'll fix that in the next release:

https://feedback.objo.dev/bug/105

einhugur

Thanks

I also see now when checking again in the IDE why I was not able to make constructor.

So I was using the top level menu the Insert menu, that one has no Add constructor:

But I now found the Add button under the File menu and that one has it.

Garry

einhugur

So the missing entry in the Insert menu is an easy fix - done for the next release: https://feedback.objo.dev/bug/107

The introspection bug needs a bit more investigating - leave it with me: https://feedback.objo.dev/bug/111

einhugur

So this one here works:

`Var p1 As Person = New Person()

Var ti As TypeInfo = TypeOf(p1)

Var p2 As Object = ti.CreateInstance()`

But this one here compiles but crashes:

`Var ti As TypeInfo = TypeOf(Person)

Var p2 As Object = ti.CreateInstance()`

So what I am getting at here is basically if you have Generic method that returns T (once the bug for that is fixed)........then how would you create instance of the T ?

Or if you have JSON serializer which has complex Struct, say Person which then has Array of addresses, you can read from the Person type that it has addresses but you never have instance of Address in advance, you only really have the types, same as the case above that crashes.

einhugur

Same if I pass in empty reference to Person then I get crash.

(Empty reference to Person would be typical case for deserializer)

Var p1 As Person

Var ti As TypeInfo = TypeOf(p1)

If ti = Nothing Then
MessageBox("Ti is nothing")
End If

Var p2 As Object = ti.CreateInstance()