I'm working on a POC with cf-2021 and mongodb (atlas). Is there a best practice for handling find() and findOne() results? I was working with findOne(), and if it finds a hit, then all is good, findOne() returns the document. But then I intentionally wanted to see what happens when a match is not found, and the behaviour seems strange:

var findResponse = this.findOne( query={ "_id": "mid:#mid#[invalidkey]" } );
		application.utilities.debug( module="daoI4goV5.getMerchant", text="Find #mid#", data=findResponse );

The debug line threw an exception because findResponse did not exist. Is this intentional and is there a best practice for handling this, meaning "try/catch", "isdefined()", "isnull()" (I'm not sure if the last even works, just throwing it out there)?

@dfgrumpy any ideas here my friend? I know you've got some experience in the nosql space & CF.

isDefined() or isNull() seem the most logical, but I have it engrained in my psyche that isDefined() is bad due to it being extremely inefficient.

This is not a unique issue with mongoDB. It is more how to handle referencing non-existent variables. There are a few things you can do. But for me, I would probably set a blank var to expected type first. Then later check to see if it is empty. So…

var findResponse = [];

// do something

arrayIsEmpty(findResponse);

There are a bunch of ways to handle this. This example is just one.

Interesting. But won't findResponse be unassigned from the assignment? I see your code working with a try/catch/ignore wrapper and the assignment throwing an exception, but in this case no exception is thrown. I'll give it a try...

you could add isArray() && ! arrayIsEmpty() together to make sure it is and has content.

I tried various versions of the following without joy:

var findResponse = {};
		findResponse = this.findOne( query={ "_id": "mid:#mid#x" }, projection=projection );
		application.utilities.debug( module="daoI4goV5.getMerchant", text="Find #mid#", data=isArray(findResponse)?findResponse:{} );

It keeps complaining that findResponse does not exist. Now I did find that isDefined("findReponse") does work, but the psyche thing.

This should do the trick… .

var findResponse = {};
        findResponse = this.findOne( query={ "_id": "mid:#mid#x" }, projection=projection );

        result = structKeyExists(variables, 'findResponse') ? variables.findResponse : {};

        application.utilities.debug( module="daoI4goV5.getMerchant", text="Find #mid#", data=result );
		return result;

I guess

var findResponse = this.findOne( query={ "_id": "mid:#mid#x" }, projection=projection );
		var result = isDefined("findResponse")?findResponse:{};
		application.utilities.debug( module="daoI4goV5.getMerchant", text="Find #mid#", data=result );
		return result;

will work. It'll just be confusing for future maintenance. LOL - same solution.