• 嵌套对象

    嵌套对象

    Immutable.Map以浅的方式包装对象，这意味着如果你有一个对象的属性绑定到可变类型，那么这些属性可以被改变。

    1. let movie = Immutable.Map({
    2.     name: 'Star Wars',
    3.     episode: 7,
    4.     actors: [
    5.         { name: 'Daisy Ridley', character: 'Rey'},
    6.         { name: 'Harrison Ford', character: 'Han Solo' }
    7.     ],
    8.     mpaa: {
    9.         rating: 'PG-13',
    10.         reason: 'sci-fi action violence'
    11.     }
    12. });
    14. movie.get('actors').pop();
    15. movie.get('mpaa').rating = 'PG';
    17. console.log(movie.toObject());
    19. /* writes
    20. { name: 'Star Wars',
    21.   episode: 7,
    22.   actors: [ { name: 'Daisy Ridley', character: 'Rey' } ],
    23.   mpaa: { rating: 'PG', reason: 'sci-fi action violence' } }
    24.   */

    要避免此问题，请改用Immutable.fromJS。

    1. let movie = Immutable.fromJS({
    2.     name: 'Star Wars',
    3.     episode: 7,
    4.     actors: [
    5.         { name: 'Daisy Ridley', character: 'Rey'},
    6.         { name: 'Harrison Ford', character: 'Han Solo' }
    7.     ],
    8.     mpaa: {
    9.         rating: 'PG-13',
    10.         reason: 'sci-fi action violence'
    11.     }
    12. });
    14. movie.get('actors').pop();
    15. movie.get('mpaa').rating = 'PG';
    17. console.log(movie.toObject());
    19. /* writes
    20. { name: 'Star Wars',
    21.   episode: 7,
    22.   actors: List [ Map { "name": "Daisy Ridley", "character": "Rey" }, Map { "name": "Harrison Ford", "character": "Han Solo" } ],
    23.   mpaa: Map { "rating": "PG-13", "reason": "sci-fi action violence" } }
    24. */

    所以，当你想修改movie.mpaa.rating。 你可能会想这样做：movie = movie.get('mpaa').set('rating'，'PG')。 然而，set将总是返回调用Map实例，在这种情况下返回映射绑定到mpaa键，而不是你想要的电影。 我们必须使用setIn方法来更新嵌套属性。

    1. let movie = Immutable.fromJS({
    2.     name: 'Star Wars',
    3.     episode: 7,
    4.     actors: [
    5.         { name: 'Daisy Ridley', character: 'Rey'},
    6.         { name: 'Harrison Ford', character: 'Han Solo' }
    7.     ],
    8.     mpaa: {
    9.         rating: 'PG-13',
    10.         reason: 'sci-fi action violence'
    11.     }
    12. });
    14. movie = movie
    15.   .update('actors', actors => actors.pop())
    16.   .setIn(['mpaa', 'rating'], 'PG');
    18. console.log(movie.toObject());
    20. /* writes
    21. { name: 'Star Wars',
    22.   episode: 7,
    23.   actors: List [ Map { "name": "Daisy Ridley", "character": "Rey" } ],
    24.   mpaa: Map { "rating": "PG", "reason": "sci-fi action violence" } }
    25. */

    我们还添加了一个对Map.update的调用，与set不同，它接受一个函数作为第二个参数，而不是一个值。 此函数接受该键处的现有值，并且必须返回该键的新值。