Operators

Arithmetic operators

| Operator | Meaning | | -------- | ----------------------------------------------------- | | ~/ | Divide, returning an integer result | | % | Get the remainder of an integer division (modulo) |

Equality and relational operators

To test whether two objects x and y represent the same thing, use the == operator.

1. If x or y is null, return true if both are null, and false if only one is null.
2. Return the result of invoking the == method on x with the argument y. (That’s right, operators such as == are methods that are invoked on their first operand.)

Type test operators

| Operator | Meaning | | -------- | -------------------------------------------------- | | as | Typecast | | is | True if the object has the specified type | | is! | True if the object doesn’t have the specified type |

Use the as operator to cast an object to a particular type if and only if you are sure that the object is of that type. Example:

(employee as Person).firstName = 'Bob';

If employee is null or not a Person, the first example throws an exception.

If you aren’t sure that the object is of type T, then use is T to check the type before using the object.

if (employee is Person) {
  // Type check
  employee.firstName = 'Bob';
}

Assignment operators

// Assign value to a
a = value;
// Assign value to b if b is null; otherwise, b stays the same
b ??= value;

Cascade notation

Cascades (.., ?..) allow you to make a sequence of operations on the same object.

var paint = Paint()
  ..color = Colors.black
  ..strokeCap = StrokeCap.round
  ..strokeWidth = 5.0;


// The previous example is equivalent to this code
var paint = Paint();
paint.color = Colors.black;
paint.strokeCap = StrokeCap.round;
paint.strokeWidth = 5.0;

If the object that the cascade operates on can be null, then use a null-shorting cascade (?..) for the first operation.

var button = querySelector('#confirm') // Get an object.
  ?..text = 'Confirm' // Use its members.
  ..classes.add('important')
  ..onClick.listen((e) => window.alert('Confirmed!'));

// The previous code is equivalent to the following:

var button = querySelector('#confirm');
button?.text = 'Confirm';
button?.classes.add('important');
button?.onClick.listen((e) => window.alert('Confirmed!'));