Often you may need to display some text or calculate a value in a dynamic fashion. For example, you may want to show different text in a field based on what the user has previously answered. Or maybe you have a product order Form that should calculate the total amount to pay. This is where the Dynamic Value property found on most form fields comes in handy. Dynamic Values allow you to create a formula that generates or calculates a result that is assigned as the given field's answer.
So, for example, imagine you have the following Form fields:
"Enter Product Name" - a Text field with Data Name of productName
"Enter Product Cost" - a Number field with Data Name of productCost
"Enter Number of Items" - a Number field with Data Name of numberItems
{{productCost}} * {{numberItems}} * 1.10
What we've done so far is add a hidden field (a field the app user will never see) which will store the result of the formula calculation. The formula is applying a 10% tax rate to the product cost amount. This is the first example of how you can use the Dynamic Value property to calculate results.
Now we're going to use Dynamic Value again to display a message to the app user. We want to summarize their order details using a read-only Text field.
concat('You ordered ', {{numberItems}}, ' of ', {{productName}}, '. Total (including tax) is: ', {{totalIncludingTax}})
What we're doing with the above formula is building up dynamic text by concatenating together pieces of text. The concat() function is used to build up the final text from the values from the various fields (the {{dataName}} bits).
See the Creating a Formula page to learn more about how a formula works.