About Expressions

Introduction

Tip: To better understand how Expressions work, check out the Use Expressions page in the How To section.

Expressions are comprised of several operations allowing you to transform, modify, and compute the data within an app in order to return an output result. Expressions can be used in several scenarios, such as:

• Bind to variables, process output, and other control values from the resources panel.
• Concatenate strings using the & symbol.
• Perform comparative operations.
• Create logical operators within comparative operations.
• Set control values through the If function added to comparative operations.
• Perform arithmetic operations with the help of expressions.
• Declare static data such as "String", true/false, 123, etc or static lists of primitives such as a list of strings.
• Control hidden, disabled, font/background color properties.
• Reference a selected record or field on a record from another control.

Configuring Expressions

The following operations can be used when configuring expressions:

• Functions
• Named Operators

Functions

The following functions are made available for Apps:

Function	Description
And, Or, Not	The And function returns true if all arguments are true. The Or function returns true if any of the arguments are true. The Not function returns true if its arguments is false, and returns false if its argument is true.
Concat	Combines multiple strings into a single string
Contains	Returns true if a string contains a text fragment.
EndsWith	Returns true if a string ends with a text fragment.
If	Returns one value if a condition is true and another value if not.
IsBlank	Checks for a blank value.
Length	Returns the length of a text string.
StartsWith	Returns true if a string starts with a text fragment.

Operators

In addition to functions, Apps expressions also supports mathematical and conditional operators. For supported operators, see the table below.

Category	Operator
Additive expression	+, -
Atomic expression	(), Literal, Variable, Functions
Comparison expression	<, <=, >, >=, in
Concatenation expression	&
Equality expression	==, !=
Exponentiation expression	^
Logical expression	&&, and, AND, | |, or, OR
Multiplicative expression	*, /, %
Unary expression	!, not, NOT, unary +, unary -

Where Can Expressions Be Used

Expressions can be used for the following:

• Controls
• Rules

Controls

Expressions are enabled for hidden and disabled properties for the following controls and their display values:

• Button - Text (icon not supported)
• Checkbox - Label, Checked
• DatePicker - Hint Text
• Dropdown - Hint Text, Default Selected
• Switch - Label, On
• Text Area - Default Text, Hint Text
• Textbox - Default Text, Hint Text
• Label - Text
• Header - Text

• Image - URL

Note: When used on control properties, expressions are re-evaluated at runtime if any of their dependent values changes.

Rules

Rules are used to enable conditional logic. You can use expressions on the following rules:

• If - Compare, Group
• Open URL - URL
• Show Message - Title, Message
• Show/hide spinner - Message
• Start process - Input override

• Set Value - Value

Note: Expressions are not reevaluated continuously when used in rules, only at the time that the rule is triggered.