遵循良好的约定，以与operator=的内置类型的行为保持一致.

That is a good convention to follow to be consistent with the behavior of operator= for built-in types.

对于内置类型，您可以执行以下操作:

With built-in types you can do something like this:

int a, b, c;
// ...
a = b = c = 10;

如果您不将引用返回给*this，则您的类型将不支持分配链.

If you do not return the reference to *this, the assignment chain won't be supported by your type.