Put query results into custom object instead of generic sObject

Question

I've seen in a few places it seems likes people are directly mapping their query over to a custom apex object. E.g.

MyObject myObject = [SELECT fields FROM object WHERE cond];

Is this possible? If so, what does my class need to look like for everything to map correctly?

Answer 1

Yes, this is actually very common, but with SObjects instead of Apex classes.

I have a feeling that if you look harder at those examples, they'll all be SObjects like Account, Contact, SomeCustomObject__c, etc...

While the official documentation does say that a SOQL query will return a List<SObject>¹, the result of a SOQL query can be automatically converted to a List of a more specific type.

For example, the following is very common (and perfectly valid)
List<Opportunity> myOpps = [SELECT Id FROM Opportunity LIMIT 10];

While not really advised², you can extend this to assigning a single variable of your target SObject type (provided that your query returns exactly one record)

^{1: ...unless you throw in a GROUP BY clause and/or use some aggregate functions like SUM(), in which case the query will return a List<AggregateResult>
2: Assigning a query to a single variable instead of a collection will cause an exception if your query returns anything other than one row. 0 rows or 2+ rows = error. The safest way to go about this is to always assign the result of a query to a collection}