How to use expressions in OutSystems to format text or compute display values?

Using Expressions in OutSystems to Format Text or Compute Display Values

Expressions in OutSystems are powerful tools for formatting text and computing display values dynamically within your applications. This guide provides a comprehensive, step-by-step process to effectively use expressions in OutSystems to manipulate and present your data as needed.

Prerequisites

• An OutSystems account with access to an OutSystems development environment.
• Basic understanding of the OutSystems platform, particularly how to navigate the Service Studio.
• Familiarity with basic programming concepts such as variables, data types, and expressions.

Understanding Expressions in OutSystems

• Expressions are used to perform operations on data and are evaluated to produce a value.
• They can handle operations like arithmetic calculations, string manipulations, and logic comparisons.
• Expressions are evaluated at runtime, allowing your application to dynamically adapt values for display.

Creating an Expression

• Open your OutSystems Service Studio and navigate to the screen where you wish to use an expression.
• Drag and drop an expression widget from the toolbox onto your screen.
• In the properties panel, click the "Value" property to open the expression editor.

Formatting Text with Expressions

• Use expressions to concatenate strings, convert data types, or apply custom formats.
• For example, to display a formatted string with a user's first and last name, use an expression like:

  "Hello, " + User.FirstName + " " + User.LastName

• Control the display format of numbers and dates using functions like FormatDecimal or FormatDateTime:

  FormatDecimal(1234.5, "##,###.00")

  FormatDateTime(CurrentDate(), "yyyy-MM-dd")

Computing Display Values

• Expressions can perform calculations to display computed results directly on the UI.
• For arithmetic operations, use basic operators (+, -, \*, /):

  TotalPrice = Quantity \* UnitPrice

• Utilize conditional logic with expressions using the IF function:

  If(Stock > 0, "In Stock", "Out of Stock")

Example Usage in a Web Application

• Create an input form with fields for user's details such as name and age.
• Add an expression widget to show a personalized message:

  "Welcome, " + InputName + "! You are " + IntegerToText(InputAge) + " years old."

Testing and Debugging Expressions

• Use the debugger tool in OutSystems to step through the application and see how expressions are evaluated.
• Inspect the runtime values of variables and expression results to ensure correctness.
• Modify expressions as needed to fix any logical or formatting issues encountered during testing.

Deploying Your Application with Expressions

• Ensure that all expressions correctly handle undefined or unexpected data inputs.
• Test user interactions on different devices and browsers to verify consistent expression evaluation and display.
• Deploy your application to a production environment once expressions are working flawlessly.

By following these steps, you can effectively use expressions in OutSystems to format text and compute display values. This allows you to create dynamic and responsive user interfaces that enhance the overall user experience in your applications.