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CreateUiDefinition logical functions

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These functions can be used in conditional expressions. Some functions might not support all JSON data types.

and

Returns true if all the parameters evaluate to true. This function supports two or more parameters only of type boolean.

The following example returns true:

"[and(equals(0, 0), equals('web', 'web'), less(1, 2))]"

The following example returns false:

"[and(equals(0, 0), greater(1, 2))]"

coalesce

Returns the value of the first non-null parameter. This function supports all JSON data types.

Assume element1 and element2 are undefined. The following example returns "Contoso":

"[coalesce(steps('demoStep').element1, steps('demoStep').element2, 'Contoso')]"

This function is especially useful in the context of optional invocation that happens due to user action after the page loads. An example is if the constraints placed on one field in the UI depend on the currently selected value of another, initially non-visible field. In this case, coalesce() can be used to allow the function to be syntactically valid at page load time while having the desired effect when the user interacts with the field.

Consider this DropDown, which allows the user to choose from several different database types:

{
  "name": "databaseType",
  "type": "Microsoft.Common.DropDown",
  "label": "Choose database type",
  "toolTip": "Choose database type",
  "defaultValue": "Oracle Database",
  "visible": "[bool(steps('section_database').connectToDatabase)]""constraints": {
    "allowedValues": [
      {
        "label": "Azure Database for PostgreSQL",
        "value": "postgresql"
      },
      {
        "label": "Oracle Database",
        "value": "oracle"
      },
      {
        "label": "Azure SQL",
        "value": "sqlserver"
      }
    ],
    "required": true
  },

To condition the action of another field on the current chosen value of this field, use coalesce(), as shown here:

"regex": "[concat('^jdbc:', coalesce(steps('section_database').databaseConnectionInfo.databaseType, ''), '.*$')]",

This functionality is necessary because the databaseType is initially not visible and therefore doesn't have a value, which causes the entire expression to not evaluate correctly.

equals

Returns true if both parameters have the same type and value. This function supports all JSON data types.

The following example returns true:

"[equals(0, 0)]"

The following example returns true:

"[equals('web', 'web')]"

The following example returns false:

"[equals('abc', ['a', 'b', 'c'])]"

greater

Returns true if the first parameter is strictly greater than the second parameter. This function supports parameters only of type number and string.

The following example returns false:

"[greater(1, 2)]"

The following example returns true:

"[greater('9', '10')]"

greaterOrEquals

Returns true if the first parameter is greater than or equal to the second parameter. This function supports parameters only of type number and string.

The following example returns true:

"[greaterOrEquals(2, 2)]"

if

Returns a value based on whether a condition is true or false. The first parameter is the condition to test. The second parameter is the value to return if the condition is true. The third parameter is the value to return if the condition is false.

The following sample returns yes.

"[if(equals(42, mul(6, 7)), 'yes', 'no')]"

less

Returns true if the first parameter is strictly less than the second parameter. This function supports parameters only of type number and string.

The following example returns true:

"[less(1, 2)]"

The following example returns false:

"[less('9', '10')]"

lessOrEquals

Returns true if the first parameter is less than or equal to the second parameter. This function supports parameters only of type number and string.

The following example returns true:

"[lessOrEquals(2, 2)]"

not

Returns true if the parameter evaluates to false. This function supports parameters only of type Boolean.

The following example returns true:

"[not(false)]"

The following example returns false:

"[not(equals(0, 0))]"

or

Returns true if at least one of the parameters evaluates to true. This function supports two or more parameters only of type Boolean.

The following example returns true:

"[or(equals(0, 0), equals('web', 'web'), less(1, 2))]"

The following example returns true:

"[or(equals(0, 0), greater(1, 2))]"

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