Query/disconnect a signal-slot connection. The connection class represents a connection between a Signal and a Slot. It is a lightweight object that has the ability to query whether the signal and slot are currently connected, and to disconnect the signal and slot. It is always safe to query or disconnect a connection. Sets the currently represented connection to the NULL connection. !this->connected(). Will not throw. const connection& this references the connection referenced by other. Will not throw. const connection& this references the connection referenced by other. Will not throw. void If this->connected(), disconnects the signal and slot referenced by this; otherwise, this operation is a no-op. !this->connected(). bool true if this references a non-NULL connection that is still active (connected), and false otherwise. Will not throw. void bool true connected() blocked() == should_block Will not throw. void connected() !blocked() Will not throw. bool true if the associated slot is either disconnected or blocked, false otherwise. Will not throw. void const connection& Swaps the connections referenced in this and other. Will not throw. bool const connection& true if this and other reference the same connection or both reference the NULL connection, and false otherwise. Will not throw. bool const connection& true if the connection referenced by this precedes the connection referenced by other based on some unspecified ordering, and false otherwise. Will not throw. void connection& connection& x.swap(y) Will not throw. noncopyable Exposition only Limits a signal-slot connection lifetime to a particular scope. const connection& this references the connection referenced by other. Will not throw. If this->connected(), disconnects the signal-slot connection. void If this->connected(), disconnects the signal and slot referenced by this; otherwise, this operation is a no-op. !this->connected(). bool true if this references a non-NULL connection that is still active (connected), and false otherwise. Will not throw.