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vasudevamurthym7396
July 3, 2023
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Assignment to local variables in Expression rule

  • July 3, 2023
  • 9 replies
  • 0 views

Hi,

I'm trying to save an array value to a local variable, it looks like getting saved, but when I check for the length of the local variable, I'm getting as 0. Where as when I save the same array during declaration of the local variable, I'm getting the length as expected. 

What I'm missing here ? what is the proper way of saving into local variables after declaring them. I've tried using a!save() but no luck.. :( 

Below are the snaps for your reference.

Assigning array after initialization 

Assigning array during initialization

 

TIA :)

Best answer by mikes0011

There are mainly only 2 places where you can "assign a value" to a local variable:

1) at declaration

2) as the result of a user interaction in an interface component

Seeing as this is an expression rule, and therefore #2 is irrelevant, you will need to assign the value at declaration (#1). 

This is the most important concept here: There is no such thing, in Appian's expression language, as "define a blank local variable then in a later line of code give it a new value".  If you know its initial value, then you will assign it at creation time.

9 replies

mikes0011
mikes0011Answer
Brainy
July 3, 2023

There are mainly only 2 places where you can "assign a value" to a local variable:

1) at declaration

2) as the result of a user interaction in an interface component

Seeing as this is an expression rule, and therefore #2 is irrelevant, you will need to assign the value at declaration (#1). 

This is the most important concept here: There is no such thing, in Appian's expression language, as "define a blank local variable then in a later line of code give it a new value".  If you know its initial value, then you will assign it at creation time.

    V
    vasudevamurthym7396Author
    July 3, 2023

    Thanks Mike for your input. 

      If you know its initial value, then you will assign it at creation time. --  what if I don't know the value of the variable during initialization and the value would come after initialization as a result of some equation like we do in traditional programming. how to handle such scenarios.

    mikes0011
    mikes0011
    Brainy
    July 3, 2023
    the value would come after initialization as a result of some equation

    You would declare its value after any other calculations (usually declared as their own local variables) on which it depends.

      mathieud0001
      mathieud0001
      Brainy
      July 3, 2023

      I think maybe having that variable being the key in the dictionary might be doing weird things.

      Try this:

      a!localVariables(
  local!parts: {
    a!map(
      partName: "part1",
      quantity: 1,
      unitCost: 1
    ),
    a!map(
      partName: "part2",
      quantity: 1,
      unitCost: 1
    )

  },
  {
    parts: local!parts,
    length: length(local!parts)
  }
)

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