Sort array of objects by one property of nested object

This is the part of the code that causes an error

Sell::getClient.name

Your can create a reference to a (static or non-static) method of an arbitrary object of a particular type. A reference to the getClient method of any object of Sell type looks like this :

Sell::getClient

But method references are not objects and don't have members to access. With this code you are trying to access a member variable of the reference (and can't)

Sell::getClient.name

Also, method references are not classes so you can't get another method reference from them. You couldn't do something like that if you tried :

Sell::getClient::getName

Correct syntax for your particular case was provided by @mlk :

1. x -> x.getClient().name
2. Sell::getClientName (doesn't have to be a static method)