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tip

References:

Tutorial:

Extra

=> Arrow Syntax for function { return ...; }​

This arrow syntax is a way to define a function that executes the expression to its right and returns its value.

bool hasEmpty = aListOfStrings.any((s) {
  return s.isEmpty;
});

is same as

bool hasEmpty = aListOfStrings.any((s) => s.isEmpty);

Null safety​

declaring variables supporting null​

int? x = null;
int? a; /// it ahs null as default value

null aware operators ??= & ??​

Dart offers some handy operators for dealing with values that might be null. One is the ??= assignment operator, which assigns a value to a variable only if that variable is currently null:

int? a; // = null
a ??= 3;
print(a); // <-- Prints 3.

a ??= 5;
print(a); // <-- Still prints 3.

Another null-aware operator is `??`, which returns the expression on its left unless that expression’s value is null, in which case it evaluates and returns the expression on its right:
print(1 ?? 3); // <-- Prints 1.
print(null ?? 12); // <-- Prints 12.

Conditional property access​

conditional member access operator ?.

myObject?.someProperty ⏩ means (myObject != null) ? myObject.someProperty : null

// Example::
// This method should return the uppercase version of `str`
// or "null" if `str` is null.
String? upperCaseIt(String? str) {
  return str?.toUpperCase();
}
tip
myObject?.someProperty

same as

(myObject != null) ? myObject.someProperty : null

Cascade ..​

class User {
  String name, email;
  Address address;
  void sayHi() => print('hi, $name');
}

class Address {
  String street, suburb, zipCode;
  void log() => print('Address: $street');
}

void main() {
  User()
   ..name = 'Alex'
   ..email = 'alex@example.org'
   ..address = (Address()
     ..street = 'my street'
     ..suburb = 'my suburb'
     ..zipCode = '1000'
     ..log())
   ..sayHi();
}
myList..add("item1")..add("item2")…..add("itemN");
⏬               ⏬           ⏬ /// can be easily written as
myList.add("item1").add("item2")….add("itemN");
//cascading operator discards the result, and returns the original receiver 'myList'
Another Example of Cascade

class Node {
String key;
Node(this.key);
Node left;
Node right;
}


void main() {
Node right = new Node('e');
Node root = new Node('root')
  ..left = (new Node('a')
    ..left = (new Node('b')
      ..left = new Node('c')
      )
      ..right = Node('d')
  )
  ..right = right;
print(root);
}