Free cookie consent management tool by TermsFeed choose() Function
choose() Function

Check out the new logical function, a!match(). It does everything choose() does but with additional flexibility so you can simplify your conditional logic without using an index.

Function

choose( key, choice1, choiceN )

Evaluates the choice argument at the given index and returns the result.

See also:

  • a!match(): Allows specifying a series of condition pairs using equal and then, or whenTrue and then. Can often achieve more complex logic than choose().
  • wherecontains(): Returns an index given a list of values and a value to find within the list; often used in combination with choose() to determine the index.
  • index(): Similar to choose(), index() returns an item at a certain index within a list. Usually used for static lists instead of expressions.

Parameters

Keyword Type Description

key

Number (Integer)

The one-based index that selects which choice argument to evaluate and return.

choice1

Any Type

The first of n possible expressions, where n must be >= 1. Only the selected value is evaluated.

choiceN

Any Type

An unlimited number of expressions.

Returns

Any Type

Usage considerations

Casting and returning boolean values

  • The key parameter is always cast to an integer to identify the choice.
  • If the value cannot be cast to an integer, the function returns an error.

Working with nulls

  • If the selected choice evaluates to null, no error occurs and null will be returned.
  • The key must be a number between 1 and the number of choices. It cannot be null.

Using lists

  • The items to evaluate must be provided as separate arguments. If a list is provided as an argument, the entire list is returned as the result.
  • The key parameter cannot be a list of values.

Evaluation order

  • Unlike most functions, choose() does not evaluate all its arguments. First the key is evaluated, then the corresponding choice argument.
  • Only one choice argument is evaluated. Use choose to avoid calling potentially costly expressions whose results would be discarded.

Other tips

When choosing values from a static list, the index() function is often easier to use. For example, both of the following examples will return the same output:

1
2
3
4
5
6
choose(
  2,
  "Low",
  "Medium",
  "High"
)
1
2
3
4
5
index(
  {"Low", "Medium", "High"},
  2,
  "Unknown"
)

However, the example using index() is far more common because the list of values can come from a single variable or constant rather than each value being provided in a separate argument. In addition, if an index value of 4 is provided in the examples above, choose() returns an evaluation error, while index() returns the default value Unknown.

One common use for the choose() function is within a wizard pattern, since it can show each page in the wizard one at a time.

Examples

Use expressions as the choice arguments

1
choose(2,2+2,4/2,3^2)

Returns 2.

Using choose to provide a random rating

It can be useful to use the wherecontains() function in conjunction with choose(). Since wherecontains() returns a list, use the first result for the key parameter.

1
2
3
4
5
6
7
8
9
a!localVariables(
  local!rating: "Excellent",
  choose(
    wherecontains(local!rating, {"Poor","Satisfactory","Excellent"})[1],
    mod(rand() * 10, 5),
    mod(rand() * 10, 5) + 4,
    10 - mod(rand() * 10, 2)
  )
)

Choose a component to display in an interface

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
a!localVariables(
  local!selectionField: 2,
  local!value: 2,
  choose(
    local!selectionField,
    a!radioButtonField(
      label: "Radio Button",
      choiceLabels: {"One", "Two", "Three"},
      choiceValues: {1, 2, 3},
      value: local!value,
      saveInto: local!value
    ),
    a!checkboxField(
      label: "Checkbox",
      choiceLabels: {"One", "Two", "Three"},
      choiceValues: {1, 2, 3},
      value: local!value,
      saveInto: local!value
    ),
    a!dropdownField(
      label: "Dropdown",
      choiceLabels: {"One", "Two", "Three"},
      choiceValues: {1, 2, 3},
      value: local!value,
      saveInto: local!value
    )
  )
)

In this example, the checkbox field is displayed since it is the second choice argument. In addition, the radio button and dropdown fields are not evaluated.

Feature compatibility

The table below lists this function's compatibility with various features in Appian.
Feature Compatibility Note
Portals Compatible
Offline Mobile Compatible
Sync-Time Custom Record Fields Compatible

Can be used to create a custom record field that only evaluates at sync time.

Real-Time Custom Record Fields Incompatible

Custom record fields that evaluate in real time must be configured using one or more Custom Field functions.

Process Reports Compatible
Process Events Compatible
Open in Github Built: Fri, Feb 23, 2024 (09:14:07 PM)

choose() Function

FEEDBACK