Safe navigation operator

是在阅读wikipedia Pyramid of doom (programming)时，其中提及的此。

wikipedia Safe navigation operator

In object-oriented programming, the safe navigation operator (also known as optional chaining operator, safe call operator, null-conditional operator) is a binary operator that returns null if its first argument is null; otherwise it performs a dereferencing operation as specified by the second argument (typically an object member access, array index, or lambda invocation).

Examples

Swift

Optional chaining operator[12], subscript operator, and call:

let name = article?.authors?[0].name
let result = protocolVar?.optionalRequirement?()