[SalesForce] Primitive and complex data types in Apex

Thanks to the comment of @KeithC I was able to go on with my research and as a result, it seems not possible to get a primitive data-type dynamically as a string. There are concepts to come close to it by the usage of instance of or try/catch in brute-force-like manner.

Since the primitive types are just a few, this workaround with instanceof seems acceptable for all types excepts of collections.

For list, map and set actually I was not able to find a satisfactory solution. Brute-force is not a general option, because of infinite possibilities. String.valueOf() can give a clue but not very much: for set and map, it returns a serialization wrapped in {} and for list it's wrapped in ().

Thanks to the feedback of @sfdcfox to try instanceof List<object>, map<object, object>, and set<object>, we seem to be able to detect lists. Unfortunately it does not work for maps and sets. This are my results:

object o;
o = new map<string,object>{}; 
system.debug( o instanceof map<string,object> ); // ==> true
system.debug( o instanceof map<object,object> ); // ==> false
o = new list<string>{}; 
system.debug( o instanceof list<string> ); // ==> true
system.debug( o instanceof list<object> ); // ==> true : only here it works
o = new set<string>{}; 
system.debug( o instanceof set<string> ); // ==> true
system.debug( o instanceof set<object> ); // ==> false

Any better approaches for collections are welcome!

The documentation to this topic is rare, as @mast0r said.

This links were helpful for me coming to this conclusion:

• Return Name of class from instance of that class
• https://stackoverflow.com/questions/9547563/how-do-i-introspect-the-class-of-a-variable-in-apex

This fails because the Model class is an inner class. It is probably a bug, but we hit this a while back and found:

• instances of inner classes can be returned to the client but cannot be passed to the server
• instances of top level classes can be passed both ways

As per sfdcfox's comment, we most often saw an internal server error when trying to pass an instance of an inner class to an aura enabled method.

The documentation does say:

Custom classes used for component attributes shouldn’t be inner classes or use inheritance. While these Apex language features might work in some situations, there are known issues, and their use is unsupported in all cases.

Whilst this appears to be for Aura code, the LWC documentation indicates LWC has the same behaviour (see the link for "Apex" in the section entitled "Expose Apex Methods to Lightning Web Components"). So whilst it is probably a bug, they have documented to say things can go wrong if you try to use inner classes.

Something else that can cause issues is the use of @AuraEnabled public attributes in your data object, which can be remedied by switching to public properties. This MAY allow you to keep the class as an inner class, but there's no guarantee this will work in all cases. Certainly changing your inner Model class to a top level one like the following will resolve any issues:

public class Model {
    @AuraEnabled
    public String someAttribute { get; set; }
}