Setting class method callback from within object (C++)

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Your code does not compile for some typing errors and issues (no return type of testCallback, missing ; behind class etc.). If you want to remove irrelevant parts of your code before posting it please assure your code still compiles and the issue persists!!

I have compiled your given code, commenting out all the map stuff and fixing the typing error and it worked as you expected. Passing this pointer to a subscriber is perfectly valid!

Another point where your code does not compille is

testObjects["firstObject"] = newObject;

This call requires a TestObject() like, i. e. arg less constructor for your class, which it does not have in the above version. You could replace it by

testObjects.insert( std::pair<std::string, TestObject>( "firstObject", newObject  ) );

In the above code which would have the same effect but would compile in the above version as it only requires a copy constructor (TestObject( const TestObject& rhs )) which is implizitly created by the compiler. I am not sure want you are doning in your real code, but storing the class in a std::map like this can cause the above issue. If you copy a class object of a class holding a subscriber using the default copy constructor (all stl containers do internally a lot of copying) it creates a flat copy of your object. All contained class members are copied. The subscriber, however contains a pointer to its implementation, where the pointer is copied but not the implementation. This means if you copy a ros::Subscriber object you will just have to Handles for the same subscription that calls into the first callback bind to it. In your case that is the first object you created, that setup the subscriber and gave it its own this pointer. I. e. if you create a subscriber in a class giving it the this pointer and then copy the created object the subscriber handle in the copied object will still call the callback with the this pointer of the object it was copied from. If the object it was copied from then goes out of scope this will cause undefined behaviour or seg faults or if there is occasionally a 0 at the point where it believes _objectName.c_str() should be it may result in the behaviour up there.

In short: If you have a class that has a subscriber and gives it "this" and you want to pass the created class object around or store it in stl containers, use boost::shared_ptr, like:

std::map<std::string, boost::shared_ptr< TestObject > > testObjects;

and then:

boost::shared_ptr< TestObject > newObject( new TestObject("objname", n) );
testObjects["firstObject"] = newObject;