Nil Safety

Optional Chaining

Most operations on nil are not permitted, so values that can be nil often require special handling.

var maybe_obj = nil;
var value = maybe_obj.value; // Error!

Instead, the ?. operator can be used to only access the value if it is not nil.

var maybe_obj = nil;
var value = maybe_obj?.value; // nil

For Array Access

When accessing an array that could be nil, optional chaining can be combined with the get method to safely access the value.

var maybe_arr = nil;
var first = maybe_arr?.get(0); // nil

For Function Calling

Similarly to arrays, when calling functions or methods that might be nil, you can use the call method to safely call the function with its arguments.

var maybe_function = nil;
maybe_function?.call();

Map Expressions

Map expressions can be used to safely handle nil values in fluent expression.

fn modify_message(message) {
  return message.to_uppercase();
}

var obj = {{
  message = nil,
}};

var maybe_modified_message = obj
  ||o -> o.message ? Ok(o) : Err("Object missing message")|
  .map((o) -> o.message |> modified_message)
  .ok();

Similarly, optional map expressions can be used to safely operate on a nil value in a fluent expression.

var maybe_number = nil;
var number_times_two_or_zero = maybe_number?|num -> num * 2| or 0;