Safe Navigation (?.) Operator

Summary

Gets the class member if the object (left-hand side) is not null.

Syntax

identifier1 ?. identifier2

Parameters

identifier1: Any legal expression.
identifier2: Any legal expression.

Description

The safe navigation operator can be used to substitute for checking for null and undefined:

class Foo
{
    void bar() {}
}
 
Foo? foo = null;
 
// The following code (if it were legal JS++):
if (foo != null) {
    return foo.bar();
}
else {
    return null;
}
// is the same as:
foo?.bar();

The safe navigation operator applies to both existent types and nullable types.

If the object (left-hand side) of the expression evaluates to null, the null value will be returned. If the object (left-hand side) of the expression evaluates to undefined, the undefined value will be returned.

Examples

Usage with Existent Types

import System;
 
class Foo
{
    void doSomething() {
        Console.log("Something happened.");
    }
}
 
Foo[] arr = [ new Foo ];
Foo+ foo = arr[Math.random(100)];
foo?.doSomething();

Usage with Nullable Types

import System;
 
class Foo
{
    Foo? maybe() {
        if (Math.random() > 0.5) {
            return this;
        }
        else {
            return null;
        }
    }
 
    void log() {
        Console.log("Something happened.");
    }
}
 
auto foo = new Foo();
foo.maybe()?.log();