B4J Question [B4X] CreateMap and Null values

[LucaMs]

I found that CreateMap accepts Null values as well, like so:

MyMap = CreateMap("Value":Null)

but If I had something like:

MyMap = Create(Null)

Private Sub Create(Value As Map) As Map
    Return CreateMap("Value":Value)
End Sub

I would get an error: java.lang.RuntimeException: Object should first be initialized (Map) <--- Map Value, the parameter.

Obviously I got around this problem easily but I wonder if it is right for this to happen.

 

[FrostCodes]

Your Sub is accepting a Map value not an object so that's why it's crashing. Null is not a Map.

 

[Erel]

Change the type of Value to Object.

 

[LucaMs]

Your Sub is accepting a Map value not an object so that's why it's crashing. Null is not a Map.

That's not the problem, it's creating the Map that way.
You could have:

    MyMap = Create2(Null)
    Log(MyMap)'ignore

Private Sub Create2(Value As Map) As Map
    Return Value
End Sub

without getting errors.

Change the type of Value to Object.

Obviously I got around this problem easily but I wonder if it is right for this to happen.

 

[Erel]

> but I wonder if it is right for this to happen.
Yes. The "value" map is uninitialized. You cannot do anything with an uninitialized map, except of initialize it.

 

[LucaMs]

Change the type of Value to Object.

Obviously I got around this problem easily .

Setting the parameter type to Object is not a good choice; the developer needs to know what kind of data to pass.

More correctly I check that the past Map is initialized depending on whether it is or not...

Private Sub Create(Value As Map) As Map
    If Value.IsInitialized Then
        Return CreateMap("Value":Value)
    Else
        Return CreateMap("Value":Null)
    End If
End Sub

 

[LucaMs]

Yes. The "value" map is uninitialized. You cannot do anything with an uninitialized map,

?

 

[LucaMs]

Yes, now it is clearer to me; in fact, an uninitialized object is not "yet" null.

 

[LucaMs]

Yes, now it is clearer to me; in fact, an uninitialized object is not "yet" null.

No, not so much (at all, I would say ?) because even the code at post #4 should throw an exception, then.