QML: How to access a singleton in another singleton

wxfred

The context is very common in C++, for example, I have two classes A and B, and I want to invoke a static method of A within a static method of B:

class A
{
public:
    static void methodA() {}
};

class B
{
public:
    static void methodB()
    {
        A::methodA();
    }
};

In qml, I simplify the code like these:
qmldir

singleton Singleton1 Singleton1.qml
singleton Singleton2 Singleton2.qml

Singleton1.qml

pragma Singleton
import QtQuick 2.0
QtObject {
    function method1() {
        console.log("invoke method1");
    }
}

Singleton2.qml

pragma Singleton
import QtQuick 2.0
QtObject {
    function method2() {
        Singleton1.method1();
    }
}

When I invoke method2 in Singleton2, something gose wrong:

qrc:/Singleton2.qml:5: ReferenceError: Singleton1 is not defined

After googling, I add import "." to Singleton2.qml, then everything works fine until I add import "." to Singleton1.qml. It seems that if more than one singleton file uses import ".", the application will crash immediately (bug?) without any useful error information but only these:

xxx.exe exited with code -1

So, what's the correct way to access a singleton in another singleton?