Number formula that will calculate days of purchase only if the checkbox returns a true value

Question

Hello I've been trying to create a formula that will calculate days since purchase date only when the checkbox approved is checked as true. I've tried the following in a number formula.

IF(
    Approvedcheck__c = True
) 
TODAY () - Sale_Date__c

I cannot find anything online.

Answer 1

Formula Operators and Functions is a very good resource to reference.

From that, on the IF() function

Determines if expressions are true or false. Returns a given value if true and another value if false. Use

IF(logical_test, value_if_true, value_if_false) and replace logical_test with the expression you want evaluated; replace value_if_true with the value you want returned if the expression is true; replace value_if_false with the value you want returned if the expression is false.

All of those arguments are required, and the true/false results need to have the same type.

Also, <boolean value> = true can always be reduced to just <boolean value>. Likewise, <boolean value> = false can be reduced to just NOT(<boolean value>)

The general recommendation is to format formulas like code (one line only contains a single expression, indent an additional level after encountering an open parenthesis).

So what you're looking for is

IF(
    Approvedcheck__c,
    TODAY() - Sale_Date__c,
    /* The "else" value needs to be the same type, so we use 0 */
    0
)