Is it possible to use a roll up or formula field to count the number of "true" or "false" values on a boolean field of a detail record?
Example:
Account <-Master—–Detail-> My_Object__c
My_Object__c has a boolean (checkbox) field called My_Boolean__c
I want to create a field on Account Object that will tell me how many of the child objects have My_Boolean__c set to false.
Is this possible without creating a trigger or workflow?
This answer assumes that the parent child relationship between Test Plan and Sub Test Plan only goes one level deep. I created a hyperlink formula field on the Test Plan to link to the Parent record which will either be itself or Master Test Plan when available.
HYPERLINK("/"&BLANKVALUE(Master_Test_Plan__r.Id, Id), BLANKVALUE(Master_Test_Plan__r.Name, Name))
I then used this formula field to summarize the data on a Test Plan report to sum the pass and fails of the Sub Test Plans as seen in this image:
Same report with details:
The pros and cons list for rollup summary vs trigger is pretty short. In fact, you've taken care of most of the pros and cons of using a rollup summary in your question.
Rollup Summary:
Pros:
Cons:
Rollup via Trigger:
Pros:
Cons:
There are a few different ways to accomplish a rollup via trigger
[SELECT SUM(Field1__c) FROM myCustomObject__c]Personally, when I need to use a trigger to do a rollup, I favor using a SOQL query to do the heavy lifting. Doing it via SOQL takes care of most of the null checks, and saves writing the same boilerplate summing logic over and over.
The declarative rollup summary tool is probably the best choice for most people outside of using a standard rollup summary field. I haven't used it myself, and don't know how well it would play with various trigger frameworks.
Conclusion:
In your case, the decision probably comes down to the question of how likely you are to need to manage the security of both objects independently.
If you will need to manage them independently, or think it's quite likely you will need to someday, go with a trigger rollup (looking at the declarative rollup summary tool first). Putting your two objects into a Master-Detail relationship would leave you with a technical debt that would be hard to resolve.
If their security can be managed together, and it doesn't look like that will ever change, go with the standard rollup via Master-Detail relationship.
Best Answer
As you spotted, this can be done declaratively in one fell swoop!
On the Master, create a Roll-up Summary called
CountMyBoolean__cwithCOUNTUnder Filter Criteria choose 'records meeting certain criteria' and
MyBoolean__c equals True