Operator overloading question

[SamuelGr]

If we look at the following:

class test_class
{
public:
	struct variables
	{
		int var_1;
		float var_2;
	} _data;

	test_class();
	~test_class();
	
	test_class& operator=(test_class& obj_arg);
};

test_class::test_class()
{
}

test_class::~test_class()
{
}
test_class & test_class::operator=(test_class& obj_arg)
{
	this->_data.var_1 = obj_arg._data.var_1;
	this->_data.var_2 = obj_arg._data.var_2;

	return *this;
}

...

test_class instance_1, instance_2;

...

instance_1 = instance_2;

The overloaded = operator will copy the data from instance_2 to instance_1, so the operator function will be called in instance_1 with instance_2 as its arg. If my analogy is correct this far, the question is why does it return *this. I've seen multiple snippets of code do the same and I don't understand the reason for the return value, can't it just be voided?

[MrHutch]

This is necessary for chaining assignments.

For example, make your assignment operator void, create three instances then assign the last to the other two in a one-liner. It fails: https://ideone.com/bCizR4

Returning a reference to your object allows this to happen. Same code with reference returned (and an obligatory self-assignment check!) : https://ideone.com/z1ZELL

[SamuelGr]

Ah, I understand now.

Thank you very much :)