/**
   * Copyright (c) 2019 formation-dart-flutter. All rights reserved
   *
   * REDISTRIBUTION AND USE IN SOURCE AND BINARY FORMS,
   * WITH OR WITHOUT MODIFICATION, ARE NOT PERMITTED.
   *
   * DO NOT ALTER OR REMOVE THIS HEADER.
   *
   * Author     : rushio consulting
   */

// main() - The special entry point, required, top-level function where app execution starts.
// This is where the app starts executing.
// Returns void and has an optional List<String> parameter for arguments.
main(List<String> args) {
  print('Result with ??');
  print(nullaware_1(null));
  print(nullaware_1(456));
  print('----------------');

  //
  print('Result with ??=');
  print(nullaware_2(1234, 0909));
  print(nullaware_2(null, 0909));
  print('----------------');

  //
  print('Result with ?.');
  print(nullaware_3("je dois être en uppercase"));
  print(nullaware_3(null));
  print('----------------');

  //
  print('Result with ...?');
  print(nullaware_4([1, 2, 3, 4], null));
  print(nullaware_4([1, 2, 3, 4], [5, 6, 7]));
  print('----------------');
}

// ??
// Use ?? when you want to evaluate and return an expression
// IFF another expression resolves to null
// ((x) => x == null ? otherExp : x)(exp)
//
// Example
int nullaware_1(int input) => input ?? 12345;

// ??=
// Use ??= when you want to assign a value to an object IFF
// that object is null. Otherwise, return the object.
// Assign the value only if the variable is null
//
// Example
int nullaware_2(int firstValue, int secondValue) {
  int result = firstValue;
  result ??= secondValue;
  return result;
}

// ?.
//Use ?. when you want to call a method/getter on an object IFF
// that object is not null (otherwise, return null).
// ((x) => x == null ? null : x.method())(obj)
// You can chain it
// obj?.child?.child?.getter
//
// Example
String nullaware_3(String firstValue) => firstValue?.toUpperCase();

// ...? Spread Operator with null aware [dart 2.3]
//
//
/*
    List numbers = [];
    numbers.addAll(lowerNumbers);
    if(upperNumbers != null){
    numbers.addAll(upperNumbers);
    }
  */
List<dynamic> nullaware_4(List<dynamic> lowerList, List<dynamic> upperList) =>
    [...lowerList, ...?upperList];