difference between Property & index function?

RE: difference between Property & index function?

Stefan Helzle — Sun, 10 Dec 2023 09:43:35 GMT

My respect for replying to a six year old conversation, explaining the same topic a fourth time.

There is a small mistake in your code snippet. A "property!" domain does not exist in Appian.

RE: difference between Property & index function?

karthik0002 — Sat, 09 Dec 2023 14:41:05 GMT

The Property() function is used for accessing fields or properties of a data type.

The Index() function is used for retrieving elements from a list or array based on their position.

For Example:

a!localVariables(
  local!employee: a!recordType(
    field1: "John",
    field2: "karthik"
  ),
  local!employeeList: {"Alice", "Bob", "Charlie"}
),
a!section(
  a!textField(
    label: "First Name:",
    value: property!employee.field1
  ),
  a!textField(
    label: "Second Name:",
    value: index(local!employeeList, 1)
  )
)

RE: difference between Property & index function?

Narmada — Mon, 21 May 2018 11:26:39 GMT

Hi Devanshum,

index( array, index, [default] )- It takes in an array in a index and returns the value with that location. Index() is more graceful to handle error's.
property( msg!properties, nameOfProperty, [valueIfMissing] )-Example:-property(msg!properties,"name","no name was sent") returns no name was sent when the name property is not received in a message.

Warm Regards
Narmada.P

RE: difference between Property & index function?

ravalik — Mon, 21 May 2018 07:15:58 GMT

Hi devanshum,
index( array, index, [default] ): Returns array [index] if it is valid else returns default value.
For example:index({10, 20, 30}, 2, 1) returns 20.
Retrieving the value of a CDT field using the field name as the index argument: index(topaginginfo(1, 10), "startIndex", 0) -Returns 1

property( msg!properties, nameOfProperty, [valueIfMissing] ): Returns anytype
For Example: property(msg!properties,"someStringProperty","Missing Text") -Returns "Missing text" if some string property doesn't exist.

Thanks,
ravalik

RE: difference between Property & index function?

Mike Schmitt — Fri, 18 May 2018 20:15:33 GMT

Interesting - I can reproduce the unexpected behavior described on that thread even now in 18.1; also of note, index() and property() both return the exact same unexpected result.

RE: difference between Property & index function?

rajats246 — Fri, 18 May 2018 20:06:52 GMT

Hi philb ,
I faced the same issue with index function.It works fine with null or "" as third parameter.SO as an alternative we can just add the curly brackets outside the index function.

RE: difference between Property & index function?

PhilB — Fri, 27 Apr 2018 10:44:46 GMT

There's also a discussion here regarding some of the possible unexpected behaviour when using index() in certain ways.

RE: difference between Property & index function?

Mike Schmitt — Thu, 26 Apr 2018 19:25:01 GMT

Both functions do the same thing in the same way, as is (vaguely) noted in the documentation.

However, I strongly recommend as a Best Practice, to use them separately, as follows:

property() when looking up i.e. a dot property of a CDT or Dictionary, as in property(ri!myCdt, "userId", null()) to try to get the "userId" dot property
index() when looking up an array index, as in index(ri!myArray, 5, null()) to try to find the 5th member of the array, and if the array isn't that long, return null.

This is most important to me since it makes it dramatically easier to read through code afterwards if you're not having to guess whether this "index()" call is trying to find a property or an array index, which can get pretty messy especially when the functions are nested.

RE: difference between Property & index function?

Robert Shankin — Thu, 26 Apr 2018 16:49:32 GMT

Details on each of are provided in Appian documentation: