Default value is considered blank

[LamaX (Nico)]

Hello !

I’ve met several times this problem. I thought the default value was a great tool to avoid some ‘Assign’ activities but it seems it doesn’t.

My problem is the following:

I have a string variable called A with a default value equals to “First_Name”+“_”+B
B is a string variable aswell. It doesn’t have a default value.
So I’ve set an input dialog activity to assign a string value to variable B. Let’s say B = “Something”.

Since I’ve said that the default value is “First_Name”+“_”+B, I’m expecting that when I’m using the string variable A, its value is “First_Name_Something”.

→ I do not use an assign activity to set A.

Actually, the output of A is First_Name_, ignoring the default value.

And I verified the B value with a write line activity (which has got the correct value I’ve set).
Looks like the default value is not supporting dynamic values but only hardcode.

So my question is : why does the default value of A is not taken into account the B value ?

Thank you very much

[vrdabberu (Varunraj Dabberu)]

Hi @LamaX

Can you share the workflow for better understanding?

Regards

[ppr (Peter Preuss)]

Lets assume the following

Variable definition and orders (similar to your input change case)

And a first Dump / Inspection

We can see that a change on B is not doing change on A. Similar as we had understood your problem description.

We do feel that the Assignment in VarA DefaultValue is using B byValue (at the assignment it is empty) and not byReference

therefore A stays FirstName_ and is not turning to FirstName_HelloWorld

Kindly note: there are datatype (often complex datatypes. e.g. DataTable) where Assignments are setting in a way of ByRef

[LamaX (Nico)]

Thank you for your feedback !

Of course ! Here it is :
TestUiPathForum.zip (39.6 KB)
Let me know if it’s not working. I just zipped the folder as it is.

@ppr : I’m not sure to fully understand what 's the difference of using a variable “byreference” and “byvalue”.

Is there a workaround in this case ? Should I set something in the parameters ?
And what is the point of default value if it’s not possible to link variables togheter ?
Is it just for hardcoding ?

[vrdabberu (Varunraj Dabberu)]

Hi @LamaX

In the above image the A is initialized with a default value. So when the code executes then It reads the variables and arguments first and then the code gets to execute. So in your scenario the B is initialized will null value so that’s why the B value printing as empty in “First_Name”+B. The input dialogue box is later so that’s why the B value is not getting printed in the First log message.

So if you want to print the B value in first log message then you need to assign a default value for B also as shown below and also the Value B should be kept above the Value A

In input dialogue box I have given the B value as Bye and here is the log messages output.

TestUiPathForum.zip (144.1 KB)

Regards

[LamaX (Nico)]

So when the code executes then It reads the variables and arguments first and then the code gets to execute.

Ok, I understand. So somehow default values are used just for hardcoding (default) values ?

Thank you very much !

[ppr (Peter Preuss)]

We assume that you are exploring concepts of development and VB.Net

@LamaX

I’m not sure to fully understand what 's the difference of using a variable “byreference” and “byvalue”.

In short: ByRef - Visual Basic | Microsoft Learn

@LamaX

And what is the point of default value if it’s not possible to link variables togheter ?

we mentioned:

@ppr

Kindly note: there are datatype (often complex datatypes. e.g. DataTable) where Assignments are setting in a way of ByRef

so it depends on a few factors if an assignment will use the value by copy (ByVal) or will use the reference to the variable (ByRef)

@LamaX

Is it just for hardcoding ?

no, as mentioned above and we often use e.g. for initializations of e.g. Lists, DataTables…