Utility Functions

Utility functions are crucial for simplifying common tasks in app development, such as performing quick calculations, formatting data, and concatenating strings.

In FlutterFlow, you can effortlessly integrate these utility functions when setting variables to value sources. This allows you to simplify processes like calculations, data formatting, and text manipulation directly within the visual builder.

FlutterFlow has the following built-in functions:

• Combine Text: A built-in function that lets you concatenate strings, making it easy to join multiple text elements together seamlessly.

• Code Expression: This feature allows you to perform simple calculations and data manipulations quickly and efficiently.

Combine Text

Oftentimes, you will encounter scenarios where you need to show two variables in a single String or Text widget. For example, in our Ecommerce Demo app, we have a price object in the following format:

"price": {
"currency": "$",
"amount": 25.50
}

However, when displaying the data in the UI, we should combine both the currency value and amount, as they make sense only together.

In such cases, we can use the Combine Text built-in function available in all value sources that take a String. You can combine any number of dynamic and static variables together, even if they are not Strings themselves. In the end, the final value is always a String since it is set to a widget that only accepts String data types.

Here is a quick demo:

Combine Text vs RichText widget

The Combine Text built-in function only allows you to combine multiple values (dynamic or static) together, with the same text style applied to all of them. If you need to combine multiple String values with different text styles for each, consider using the RichText widget.

Code Expressions

Oftentimes, you may need to quickly format data, convert a data type from one form to another, or perform a simple calculation before setting the variable to a data source, such as a widget value source.

Code Expression built-in functions can help with these tasks. A code expression is a piece of code that combines operators, variables, and/or values to produce a result. It can be used for arithmetic and logical operations, among other tasks.

To perform a code expression, open the Variable Setter dialog wherever it's possible to set a dynamic value and choose the values that will be part of the code expression.

For example, we may want to quickly calculate the discount amount of a product where the discount is 18% of the MRP of the product.

The expression would be cost - (cost * discount).

Precedence of operations

Code expressions for math operations follow typical precedence (e.g., multiplication/division before addition/subtraction), but parentheses can change the order.

In this case, the variables we need are cost and discount.

So, we create two arguments in the Code Expression dialog where they hold the value of cost and discount, assign the data type for each of the arguments, and define the return type of the final value. In this case, the return type is a double since it holds the subtotal amount.

Now you can write the code expression in the Expression field and click on Check Errors to see if the expression is valid. If it is valid, you will see the generated code for the same.

The arguments in a Code Expression can take the following properties:

DataType	Supports Nullable	Supports List
String	✅	✅
Integer	✅	✅
Double	✅	✅
Boolean	✅	✅
Colors	✅	✅

Common Examples

Here are some common expressions you can use for your business logic:

Expression	Description	Example	Return Type
contains()	Checks if a string contains a particular substring.	text1.contains(text2)	bool
split()	Splits a string into a list of substrings.	text.split(",")	List<String>
toLowerCase() or toUpperCase()	Converts all characters in a string to lowercase.	text.toLowerCase()	String
contains()	Checks if a list contains a particular element.	fruits.contains("apple")	bool
max()	Returns the larger of two numbers.	math.max(a, b)	int
toDouble()	Converts the integer to a Double.	intValue.toDouble()	double
int.parse(s)	Convert the String into an integer.	int.parse(stringValue)	int

Custom Functions

You can also use custom functions to handle slightly more complex calculations or to process a wider range of data types that are not supported in Code Expression.

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Learn more about Custom Functions.