Quick answer: what gets passed to your functions cookEggs and cookOne are references to the objects, not to the variables (which would be real pass-by-reference). The term pass-by-reference is often misused to mean pass-references-by-value: many languages only have pass-by-value semantics, where the values that are passed around are references (i.e. pointers, without the dangerous features). … Read more
To complete Gunter’s answer: the recommended way to compare lists for equality (rather than identity) is by using the Equality classes from the following package import ‘package:collection/collection.dart’; Edit: prior to 1.13, it was import ‘package:collection/equality.dart’; E.g.: Function eq = const ListEquality().equals; print(eq([1,’two’,3], [1,’two’,3])); // => true The above prints true because the corresponding list elements … Read more
Just for the sake of clarity specially for the newcomers to Flutter/Dart, here is what you need to do in order to enable this option globally in your project: In your main.dart file, add or import the following class: class MyHttpOverrides extends HttpOverrides{ @override HttpClient createHttpClient(SecurityContext? context){ return super.createHttpClient(context) ..badCertificateCallback = (X509Certificate cert, String host, … Read more
Dart constructs objects in two phases: first outside-in and then inside-out. Initializer lists are executed outside-in (from derived class to base class). After this is done, the object’s members should be initialized, the object is considered to be “constructed”, and this exists. (That’s why you can’t use this in a meaningful way in an initializer … Read more
You could use https://github.com/slightfoot/flutter_after_layout which executes a function only one time after the layout is completed. Or just look at its implementation and add it to your code 🙂 Which is basically void initState() { super.initState(); WidgetsBinding.instance .addPostFrameCallback((_) => yourFunction(context)); }
Short answer: Instead of the pre-null-safety operations var foo = List<int>(); // Now error var bar = List<int>(n); // Now error var baz = List<int>(0); // Now error use the following: var foo = <int>[]; // Always the recommended way. var bar = List.filled(1, 0); // Not filled with `null`s. var baz = List<int>.empty(); Long … Read more
There is a post on dart’s website and it explains it pretty well. Final: “final” means single-assignment: a final variable or field must have an initializer. Once assigned a value, a final variable’s value cannot be changed. final modifies variables. Const: “const” has a meaning that’s a bit more complex and subtle in Dart. const … Read more
Thanks to Dart’s factory constructors, it’s easy to build a singleton: class Singleton { static final Singleton _singleton = Singleton._internal(); factory Singleton() { return _singleton; } Singleton._internal(); } You can construct it like this main() { var s1 = Singleton(); var s2 = Singleton(); print(identical(s1, s2)); // true print(s1 == s2); // true }
This answer will cover both passing data forward and passing data back. Unlike Android Activities and iOS ViewControllers, different screens in Flutter are just widgets. Navigating between them involves creating something called a route and using the Navigator to push and pop the routes on and off the stack. Passing data forward to the next … Read more
You can use the intl package (installer) to format dates. For en_US formats, it’s quite simple: import ‘package:intl/intl.dart’; main() { final DateTime now = DateTime.now(); final DateFormat formatter = DateFormat(‘yyyy-MM-dd’); final String formatted = formatter.format(now); print(formatted); // something like 2013-04-20 } There are many options for formatting. From the docs: ICU Name Skeleton ——– ——– … Read more