Based on that simple class:

class User { String? name; int? id; }

I'm not sure what is the difference between:
var user = User();
or:
User user = User();
If someone can shed some light on this I'll be more than happy.

CodePudding user response：

There's no practical difference in this case. When you use the var keyword, the type will be inferred by the compiler, whereas declaring it as User is simply a way to explicitly define the type.

There are some cases where it would make some difference though, such as when instantiating a generic type, like List.

If you type:

var list = [1, 2, 3];

Then list will have a type of List<int>. But you might have wanted a list of doubles. In that case, you could write:

List<double> list = [1, 2, 3];

And you would be assured that list would have the type you want (though of course in this case you could also simply write var list = [1.0, 2.0, 3.0]).

It's also helpful when instantiating an empty list, since in that case there are no values in the list from which the compiler can infer the type.