Configure your app with formulas that not only calculate values and perform other tasks (as they do in Excel) but also respond to user input (as an app requires).
For example, you build a formula to determine how your app responds when users select a button, adjust a slider, or provide other input. These formulas might show a different screen, update a data source that's external to the app, or create a table that contains a subset of the data in an existing table.
You can use formulas for a wide variety of scenarios. For example, you can use your device's GPS, a map control, and a formula that uses Location.Latitude and Location.Longitude to display your current location. As you move, the map automatically tracks your location.
This topic provides only an overview of working with formulas. Browse the formula reference for more details and the complete list of functions, operators, and other building blocks you can use.
In Excel, you can enter a specific piece of data, such as the number 42 or the phrase Hello World, by typing it into a cell. That cell will always show that data exactly as you typed it. In PowerApps, you can similarly specify a piece of data that doesn't change by setting the Text property of a label to the exact sequence of characters that you want, surrounded by double quotation marks.
Select New on the File menu (near the left edge of the screen).
Under Create an app, select Phone layout on the Blank app tile.
The formula bar sits at the top of the screen.
This bar has two parts:
In the formula bar, you can see and edit properties for the selected control or for the screen if no controls are selected. You can see the name of the selected control on the Content tab:
You can change the name of the selected control in the Content tab by clicking the name.
Add a Text box control to the screen.
When you add a text box, the property list automatically shows the Text property, which drives what the control shows. By default, the value of this property is "Text".
Set the value of the Text property to "Hello World" by typing that string, surrounded by double quotes, into the formula bar:
The text box reflects this new value as you type it. The screen may show yellow exclamation-point icons while you type. These icons indicate errors, but they'll go away when you finish entering a valid value. For example, a string without double quotation marks on both ends isn't valid.
In Excel, you can show a number, such as 42, by typing it into a cell or by typing a formula that resolves to that number, such as =SUM(30,12). In PowerApps, you can achieve the same effect by setting the Text property of a control, such as a text box, to 42 or Sum(30,12). The cell and the text box will always show that number regardless of what else changes in the worksheet or the app.
Note: In PowerApps, you don't precede a formula with an equals sign or a plus sign as you do in Excel. The formula bar treats anything you type there as a formula by default. You also don't surround a formula with double quotation marks ("), as you did earlier to specify a string of text.
In the Text property of the text box, replace "Hello World" with Sum(1,2,3).
While you type, the formula bar helps you by showing the description and the expected arguments for this function. As with the final double quotation mark in "Hello World", the screen shows yellow exclamation points to indicate an error until you type the final parenthesis of this formula:
In Excel, you type =SUM(A1:A2) into a cell to show the sum of whatever values cells A1 and A2 contain. If either or both of those values change, the cell that contains the formula automatically shows the updated result.
In PowerApps, you can achieve a similar result by adding controls and setting their properties. This example shows the text box from the previous procedure and two Text input controls, named TextInput1 and TextInput2.
Regardless of what numbers you type in the input-text controls, the text box always shows the sum of those numbers because its Text property is set to this formula:
TextInput1 + TextInput2
In Excel, you can use conditional formatting to show, for example, negative values in red. In PowerApps, you use a formula that contains the If function, which behaves similarly to how it behaves in Excel.
Set the Color property of the text box to this formula:
If( Value(TextBox1.Text) < 0, Red, Black )
Note: In a formula, specify the property of a control by providing the name of the control, followed by a period, followed by the name of the property. For example, specify the Text property of TextBox1 by typing TextBox1.Text.
In TextInput1 and TextInput2, specify two numbers that, when added together, result in a negative number.
The value in the text box appears in red.
You can configure your app with formulas so that users can change your app's appearance or behavior. For example, you can create a filter to show only data that contains a string of text that the user specifies, or you can let users sort a set of data based on a certain column in the data set. In this procedure, you'll let users change the color of the screen by adjusting one or more sliders.
Remove the controls from the previous procedures, or create a blank app as you did previously, and add three slider controls to it:
Arrange the sliders so they don't overlap, add three text boxes, and configure them to show Red, Green, and Blue:
Set the Max property of each slider to 255, which is the maximum value of a color component for the RGBA function.
You can specify the Max property by selecting it on the Content tab or in the property list:
Select the screen by clicking away from any control, and then set the screen's Fill property to this formula:
RGBA( Slider1.Value, Slider2.Value, Slider3.Value, 1 )
As already described, you access control properties by using the . operator. Slider1.Value refers to the slider's Value property, which reflects where the user has placed the slider between the Min and Max values. As you type this formula, each control that it contains is color coded between the screen and the formula bar:
As you type the closing parenthesis, the screen's background will change to dark gray based on the default value of each slider, which is 50. At the moment when you finish typing the formula, it's calculated and used as the value of the background fill color. You can interact with your app while in the default workspace without needing to open Preview:
Adjust the sliders, and see how your changes affect the background color.
As each slider changes, the formula that contains the RGBA function is recalculated, which immediately changes how the screen appears.
You can use formulas not only to perform calculations and change appearance but also to take action. For example, you can set the OnSelect property of a button to a formula that includes the Navigate function. When a user selects that button, the screen that you specify in the formula appears.
You can take more than one action in a behavior formula if you separate functions with a semi-colon (;). For example, you might want to update a context variable, push data to a data source, and finally navigate to another screen.
The properties list shows properties alphabetically, but you can also view all the properties of a control, organized by category, if you select the Advanced option on the View tab:
You can edit formulas directly within this view. With the control selector at the top of the pane, you can quickly find a control to work with. And with the property search, you can quickly find a property of that control.
Initially, this view shows the most important properties. To reveal all the properties, click the down arrow at the bottom of the pane. Each control has a long list of properties that govern all aspects of the control's behavior and appearance. You can scroll through the list or search for a property by typing in the box at the top of the pane.