Why const can disappear at QMap::value(...)

[QtCrawler]

Hello,

I have some basic questions, I'm very interested in.

If I have a QMap<int,MyObject*>* and call method value on it, the method returns a pointer to a const instance of MyObject.

QMap<int,MyObject*>* myMap = new QMap<int,MyObject*>();
myMap->insert(1,new MyObject());
 
MyObject const * object_one = myMap->value(1); // const instance of myObject. I'm not allowed to call non-const methods on it.
object_one->changeMe(); //compiler will complain about it

QMap<int,MyObject*>* myMap = new QMap<int,MyObject*>();
myMap->insert(1,new MyObject());

MyObject const * object_one = myMap->value(1); // const instance of myObject. I'm not allowed to call non-const methods on it.
object_one->changeMe(); //compiler will complain about it

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but I can write it like this:

MyObject * object_one = myMap->value(1); // non-const instance of myObject. I'm allowed to call non-const methods on it.
object_one->changeMe(); //compiler wont't complain about it

MyObject * object_one = myMap->value(1); // non-const instance of myObject. I'm allowed to call non-const methods on it.
object_one->changeMe(); //compiler wont't complain about it

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And now I can mutate the instance. I want to know if this works just because of c-compatibility, if it's ok to use it like that (I would say no)?

Further I want to know how should I pass such an instance to another object which should hold the instance as mutable member (MyObject* myobject):

OtherClass(MyObject * myobject) : myobject(myobject){ }
 
MyObject const * const_object_one = myMap->value(1); // const instance of myObject. I'm not allowed to call non-const methods on it.
MyObject * object_one = myMap->value(1); // non-const instance of myObject. I'm allowed to call non-const methods on it.
 
OtherClass* other_object = new OtherClass(const_object_one);//fails
 
OtherClass* other_object = new OtherClass(object_one);//works

OtherClass(MyObject * myobject) : myobject(myobject){ }

MyObject const * const_object_one = myMap->value(1); // const instance of myObject. I'm not allowed to call non-const methods on it.
MyObject * object_one = myMap->value(1); // non-const instance of myObject. I'm allowed to call non-const methods on it.

OtherClass* other_object = new OtherClass(const_object_one);//fails

OtherClass* other_object = new OtherClass(object_one);//works

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Can I call the constructor passing the object via QMap::value, or should I use []->operator?

Thank you