What is the purpose of a double point operator in Dart?

Question

在以下代码中使用双点运算符是什么意思？

var _tabController = TabController(length: 2, vsync: this)..addListener(_onTabChange);

Answer 1

It's called cascade notation , a syntax sugar for subsequent statements of the object.

It's equivalent of:

var _tabController = TabController(length: 2, vsync:this);
_tabController.addListener(_onTabChange);

Instead writing the object name again and again, you can sequently write the statements without breaking the object assignment.

docs:https://dart.dev/guides/language/language-tour#cascade-notation