How is access to the global key in the system implemented?

In Flutter, access to a global key (GlobalKey) is done through its instance, which is usually created and stored in the widget's state or elsewhere where access is needed.

GlobalKey allows access to the state or context of the widget it is associated with. This is useful, for example, for calling methods on the state of a child widget or for managing forms.

Example of using GlobalKey to access the state of a form:

final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

// In the widget:
Form(
  key: _formKey,
  child: Column(
    children: [
      TextFormField(...),
      ElevatedButton(
        onPressed: () {
          if (_formKey.currentState!.validate()) {
            // The form is valid, continue
          }
        },
        child: Text('Submit'),
      ),
    ],
  ),
)

Here, _formKey.currentState provides access to the form's state, allowing you to call methods like validate().

Thus, access to a global key is done through its properties, such as currentState or currentWidget, depending on the task.