Get.put仅在没有示例（或已有示例被标记为脏示例）的情况下放置一个新示例。您可以通过深入研究代码来查看它。按住Ctrl键并单击put方法（至少在Android Studio中是这样），您可以查看实现。第一步是

S put<S>(S dependency,
          {String? tag,
          bool permanent = false,
          InstanceBuilderCallback<S>? builder}) =>
      GetInstance().put<S>(dependency, tag: tag, permanent: permanent);

那么在put上再做一次会导致

S put<S>(
    S dependency, {
    String? tag,
    bool permanent = false,
    @deprecated InstanceBuilderCallback<S>? builder,
  }) {
    _insert(
        isSingleton: true,
        name: tag,
        permanent: permanent,
        builder: builder ?? (() => dependency));
    return find<S>(tag: tag);
  }

深入研究_insert方法得到：

/// Injects the Instance [S] builder into the `_singleton` HashMap.
  void _insert<S>({
    bool? isSingleton,
    String? name,
    bool permanent = false,
    required InstanceBuilderCallback<S> builder,
    bool fenix = false,
  }) {
    final key = _getKey(S, name);

    if (_singl.containsKey(key)) {
      final dep = _singl[key];
      if (dep != null && dep.isDirty) {
        _singl[key] = _InstanceBuilderFactory<S>(
          isSingleton,
          builder,
          permanent,
          false,
          fenix,
          name,
          lateRemove: dep as _InstanceBuilderFactory<S>,
        );
      }
    } else {
      _singl[key] = _InstanceBuilderFactory<S>(
        isSingleton,
        builder,
        permanent,
        false,
        fenix,
        name,
      );
    }
  }

这里你可以看到如果它已经存在并且isDirty为真，或者它还不存在，那么它只会插入一个新的示例，现在我不完全确定什么时候设置isDirty，但我相信当你在应用程序中改变路线时会发生这种情况。所以第二次调用put时，你实际上是在检索之前已经放在那里的路线。现在，如果你想拥有多个示例，你可以使用Get.create(() => UserController());，后面跟着Get.find。

void main()
{
  Get.create(() => UserController());
  UserController uc1 = Get.find();
  UserModel user1=UserModel(username: 'abc', password: 'a123');
  uc1.currentuser=user1;

  //showing print abc
  print(uc1.currentuser!.username);

  UserController uc2 = Get.find();
  UserModel user2=UserModel(username: 'xyz', password: 'x123');
  uc2.currentuser=user2;

  //showing printing result=xyz
  print(uc2.currentuser!.username);

  //showing printing result=abc
  print(uc1.currentuser!.username);

}

因为您要使用put方法两次，所以如果您要更新单个示例，请遵循以下代码：

void main()
{
  final uc1=Get.put(UserController());
  UserModel user1=UserModel(username: 'abc', password: 'a123');
  uc1.currentuser=user1;

  //showing print abc
  print(uc1.currentuser!.username);

 UserController uc2 = Get.find();
  UserModel user2=UserModel(username: 'xyz', password: 'x123');
  uc2.currentuser=user2;

  //showing printing result=xyz
  print(uc2.currentuser!.username);

  //showing printing result=abc
  print(uc1.currentuser!.username);

}