Exceptions

It is better to pass the property name to the exception constructor and let the exception class define the message. It is better because:

• It's more DRY. If you have to throw that exception from another function you need to create the same message.
• Single responsibility
• Easier to test - only need to test the exception and the property name. The test will not break if you decide to change the message.
• Logging - when your exceptions connected to some logging mechanism and a tool. You can search for this specific exception and specific property name.

Naming

I think a good name for a map is a name describing the key and the value. I think values_ should be called propertyName2Value.

#Suggested Additions

• Add a specific exception to the case get is called with the wrong type
• implement operator[]

Performance

It is probably a micro-optimization but map operations runtime complexity are O(log N) where unordered_map operations are O(1).

Exceptions

It is better to pass the property name to the exception constructor and let the exception class define the message. It is better because:

• It's more DRY. If you have to throw that exception from another function you need to create the same message.
• Single responsibility
• Easier to test - only need to test the exception and the property name. The test will not break if you decide to change the message.
• Logging - when your exceptions connected to some logging mechanism and a tool. You can search for this specific exception and specific property name.

Naming

I think a good name for a map is a name describing the key and the value. I think values_ should be called propertyName2Value.

Suggested Additions

• Add a specific exception to the case get is called with the wrong type
• implement operator[]

Performance

It is probably a micro-optimization but map operations runtime complexity are O(log N) where unordered_map operations are O(1).