In practice this means we have a couple of options to test if this is happening: When QObject::connect() fails it returns false and it emits a warning which gets typically printed on the console, if you have one, or in Creator’s output pane.
The elements marked with a (*) do not fully apply to the new connection syntax, which performs checks at compile-time. Was the connection established in the first place?Ī QObject::connect() statement may fail to connect a signal to a slot for various reasons. Keeping a debug print in place is also useful to know when we have finally fixed the problem, and the slot is getting invoked as expected. Was the slot really not invoked?įirst and foremost, are we really sure that the slot was not invoked? A simple way to rule this out is by adding a debug print in the slot, or running the application in a debugger and setting a breakpoint. This blog post is a practical series of checks to help you debug these sorts of issues. There are a number of reasons why a connection may fail to be properly set up, and ultimately cause our slot not to be invoked.
All Qt developers have asked themselves at least once in their careers: “why isn’t my slot invoked?” (I’ve asked myself that question many, many times).
