IfError and IsError functions in Power Apps

[This article is pre-release documentation and is subject to change.]

Detects errors and provides an alternative value or takes action.

Note

IfError

The IfError function tests values until it finds an error. If the function discovers an error, the function evaluates and returns a corresponding replacement value and stops further evaluation. A default value can also be supplied for when no errors are found. The structure of IfError resembles that of the If function: IfError tests for errors, while If tests for true.

Use IfError to replace an error with a valid value so that downstream calculations can continue. For example, use this function if user input might result in a division by zero:

IfError( 1/x, 0 )

This formula returns 0 if the value of x is zero, as 1/x will produce an error. If x isn't zero, then 1/x is returned.

Stopping further processing

When chaining formulas together in behavior formulas, such as:

Patch( DS1, ... );
Patch( DS2, ... )

The second Patch function to DS2 will be attempted even if the Patch to DS1 fails. The scope of an error is limited to each formula that is chained.

Use IfError to do an action and only continue processing if the action was successful. Applying IfError to this example:

IfError(
    Patch( DS1, ... ), Notify( "problem in the first action" ),
    Patch( DS2, ... ), Notify( "problem in the second action" )
)

If the Patch of DS1 has a problem, the first Notify is executed. No further processing occurs including the second Patch of DS2. If the first Patch succeeds, the second Patch will execute.

If supplied, the optional DefaultResult argument is returned if no errors are discovered. Without this argument, the last Value argument is returned.

Building on the last example, the return value from IfError can be checked to determine if there were any problems:

IfError(
    Patch( DS1, ... ), Notify( "problem in the first action" );  false,
    Patch( DS2, ... ), Notify( "problem in the second action" ); false,
    true
)

Type compatibility

IfError will return the value of one of its arguments. The types of all values that might be returned by IfError must be compatible.

In the last example, Patch will return a record that isn't compatible with the Booleans used for the Replacement formulas or the DefaultResult. Which is fine, since there's no situation in which the return value from these Patch calls would be returned by IfError.

Note

While the behavior in process for a change, the types of all arguments to IfError must be compatible currently.

In the simple example described earlier:

IfError( 1/x, 0 )

The types of 1/x and 0 were compatible as both were text strings. If they're not, the second argument will be coerced to match the type of the first argument.

Excel will display #DIV/0! when a division by zero occurs.

Consider IfError with the following instead:

IfError( 1/x, "#DIV/0!" )

The above formula won't work. The text string "#DIV/0!" will be coerced to the type of the first argument to IfError, which is a number. The result of IfError will be yet another error since the text string can't be coerced. As a fix, convert the first argument to a text string so that IfError always returns a text string:

IfError( Text( 1/x ), "#DIV/0!" )

As seen above, IfError can return an error if the Replacement or DefaultResult is an error.

ErrorInfo

Within in the replacement formulas, the ErrorInfo record provides information about the error that was found. This record includes:

ErrorInfo field Type Description
Control Text string Name of the current control, used to report where the error occurred.
Kind ErrorKind enum (number) Categorized the error.
Message Text string Message about the error, suitable to be displayed to the end user.
Notify Boolean If not caught by IfError, whether an end-user notification banner should be displayed.
Property Text string Name of the current property, used to report where the error occurred.

For example, consider the following formula as a Button control's OnSelect property:

IfError( 1/0, Notify( "Internal error: " & ErrorInfo.Control & "." & ErrorInfo.Property ) )

The example formula above would display the following banner when the button is activated:

Button control activated, showing a notification from the Notify function

IsError

The IsError function tests for an error value. The return value is a Boolean true or false.

Using IsError will prevent any further processing of the error.

Syntax

IfError( Value1, Replacement1 [, Value2, Replacement2, ... [, DefaultResult ] ] )

  • Value(s) – Required. Formula(s) to test for an error value.
  • Replacement(s) – Required. The formulas to evaluate and values to return if matching Value arguments returned an error.
  • DefaultResult – Optional. The formulas to evaluate if the formula doesn't find any errors.

IsError( Value )

  • Value – Required. Formula to test for an error value.

Examples

Simple IfError

Formula Description Result
IfError( 1, 2 ) The first argument isn't an error. The function has no other errors to check and no default return value. The function returns the last value argument evaluated. 1
IfError( 1/0, 2 ) The first argument returns an error value (because of division by zero). The function evaluates the second argument and returns it as the result. 2
IfError( 10, 20, 30 ) The first argument isn't an error. The function has no other errors to check but does have a default return value. The function returns the DefaultResult argument. 30
IfError( 10, 11, 20, 21, 300 ) The first argument 10 isn't an error, so the function doesn't evaluate that argument's corresponding replacement 11. The third argument 20 isn't an error either, so the function doesn't evaluate that argument's corresponding replacement 21. The fifth argument 300 has no corresponding replacement and is the default result. The function returns that result because the formula contains no errors. 300
IfError( 1/0, Notify( "There was an internal problem" ) ) The first argument returns an error value (due to division by zero). The function evaluates the second argument and displays a message to the user. The return value of IfError is the return value of Notify, coerced to the same type as the first argument to IfError (a number). 1

Simple IsError

Formula Description Result
IsError( 1 ) The argument isn't an error. false
IsError( 1/0 ) The argument is an error. true
If( IsError( 1/0 ), Notify( "There was an internal problem" ) ) The argument to IsError returns an error value (because of division by zero). This funciton returns true, which causes the If to display a message to the user with the Notify function. The return value of If is the return value of Notify, coerced to the same type as the first argument to If (a boolean). true

Step by step

  1. Add a Text input control, and name it TextInput1 if it doesn't have that name by default.

  2. Add a Label control, and name it Label1 if it doesn't have that name by default.

  3. Set the formula for Label1's Text property to:

    IfError( Value( TextInput1.Text ), -1 )
    
  4. In TextInput1, enter 1234.

    Label1 will show the value 1234 as this is a valid input to the Value function.

  5. In TextInput1, enter ToInfinity.

    Label1 will show the value -1 as this isn't a valid input to the Value function. Without wrapping the Value function with IfError, the label would show no value as the error value is treated as a blank.

See also

Formula reference for Power Apps