But on a day of Irish rain and wind, in a dim cubicle in a corner of an office, along came Qt and a wonderful C++ world opened up, with new revelations ever since.

Add emit_for_all_but_one and emit_for methods.After so many nerves lost over all the quirks and twists and turns of C++ with OpenGL and MFC, working with C# or Java was like a breath of fresh air.

Add move-copy-constructor and move-assignment-operator.

This will allow for a clean implementation of the observer pattern. In a follow-up post I’ll present another simple class: the Property.

Using this Signal class other patterns can be implemented easily.

Both problems are easy to solve but would make this example more complex. There are two drawbacks in this simple implementation: It’s not threadsafe and you cannot disconnect a slot from a signal from within the slot callback. template class Signal Issues & next steps Any argument passed to emit() // will be passed to the given functions. You can connect functions to the signal // which will be called when the emit() method on the // signal object is invoked. A signal object may call multiple slots with the // same signature. Further below you will find two usage examples. The class is documented with comments and should be quite understandable. The emit method will accept the same argument types you declared as template parameters for the Signal class. Basically you can create signals which allow for arbitrary slot signatures. Because this class is using variadic templates you can define signals which pass any kind of data to their slots. The signal template classīelow you can find the entire class. All you need is the header I posted below. There are many libraries around (refer to the linked Wikipedia article) implementing this pattern, but it’s so easy to implement on you own that I would recommend to do this without an additional dependency. And the big plus: It can be added to your program with one simple template class! In my opinion it’s intuitive to use and produces easily readable code when used in a moderate amount. So basically it allows for event based inter-object communication. The concept is that GUI widgets can send signals containing event information which can be received by other controls using special functions known as slots. A language construct which makes it easy to implement the Observer pattern while avoiding boilerplate code.

Qt creator signals and slots