# Types

2 min read, 330 words dart types

# Explicit Typecasting

3 / 2    // 1.5
3 ~/ 2   // truncating operator

# String Interpolation

dart preferes single quotes, just like python

three single quote to write multi-line strings

# Lists

ordered iterables of objects

uses 0 based indexing
list of objects
list of multiple different types
has multiple contructors, Eg: List.empty(growable: true)
null aware spread operator ...?
dart have collection if conditional and for iteration

List<ClassName> listOfObjects = [ ClassName(), ClassName(), ClassName()]

// list of multiple types
List<Object?> complexList = [2, 'hello', true, null]

List<int> a = [1,2,3];
List<int?> b = [1,2, null];
List<int>? c = null;
List<int?>? d = [null, null];

// null aware operators
int? a = null;
print(a.isEven);
print(a?.isEven);  // call methos only if it exists
print(a!.isEven);  // asbolutely sure that object has this  method

# dart Cascading operator

dart has cascading operator, to createa computation logic pipelines of transforms

List<int> list2 = (([1,0,2]..sort()).reversed.toList()
  ..addAll([5,3,4])
  ..sort())
  .map((e) => e + 1)
  .toList();
print(list2);

# Runes

use unicodes code-points as dart string data structures

# Expressions

int first(int a) => a.isOdd ? 1 : 0

# Data structures

implement stacks, queues, trees in dart

consider using <Generics> when creating your own data structures
iterables >> lists when using asynchronous code

# questions

what is the difference between required and @required in flutter. What is the difference between them and when do we need to use them? (opens new window)

@required is just an annotation that allows analyzers let you know that you're missing a named parameter and that's it. so you can still compile the application and possibly get an exception if this named param was not passed.

How to write your own dart annotations? (opens new window)

Any class with a const constructor can be used as annotation. Eg: @override api spec (opens new window) Javascript also has @override annotations (opens new window)

Annotations work at @buildtime, @compiletime

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