rxdart - using combineLatest, the way combiner works

How does the combiner actually work?

Stream<bool> get isValid => Rx.combineLatest2(name1, mobile1, (name2, mobile2) => true);

If name1 and mobile1 are streams, then what are the types of name2 and mobile2 in brackets?

In your example, name2 and mobile2 refer to the latest content that was emitted by the streams name1 and mobile1. So your question - the types of name2 and mobile2 - depend on the streams that you give it.

I think calling them name1 and name2 actually kind of makes it a bit confusing, and perhaps it would make more sense to think of it like this:

Rx.combineLatest2(nameStream, mobileStream, (name, mobile) => ... )

To give a concrete example, imagine that name is a String and mobile is int. And imagine that what you want is a Stream of your own class called Person which has the parameter name and mobile like this:

class Person {
  String name;
  int mobile;
  
  Person({required this.name, required this.person});
}

You could combine your latest name and latest mobile to get a Stream<Person> like this:

Stream<Person> get person => 
   Rx.combineLatest2(
      nameStream, mobileStream, (name, mobile) => 
         Person(name: name, mobile: mobile));

where:

• nameStream is of type Stream<String>
• mobileStream is of type Stream<int>
• name is of type String
• mobile is of type int
• and the get function person returns Stream<Person>

You can specify your class types in the function like this:

Stream<Person> get person => 
  Rx.combineLatest2<String, int, Person>(
    nameStream, mobileStream, (name, mobile) => 
       Person(name: name, mobile: mobile));