How to Define Slots in C++


A slot online is a type of member function that can be defined in C++. When directly invoked, slots follow the same rules as normal member functions. However, slots can also be invoked by signals sent by a component. This way, a signal sent by one class to another class can cause its private slot to be invoked. Another option for using slots is to define them as virtual.

Invoke a slot

Invoke a slot method is a C++ method that executes code when it receives a signal from another object. This method has no parameters and is called only when a signal arrives. The type of signal can be either a signal that comes from a single object or one that comes from many objects. You can record multiple signals to a single slot method using a postsignal or idlesignal statement. You can create a copy of a slot method by pressing Ctrl and pressing V, or by dragging a method onto the workspace.

Invoke a slot can be a block in your application. You must make sure that the block you create is not already in use. This will block the thread until you release it. Moreover, it will make the call to a slot in a different thread. This will cause a deadlock if two threads attempt to invoke the same slot.

Invoke a slot in a signal

When using a signal in a C++ program, you can invoke a slot in that signal using the connect() method. This method accepts one or more function pointers as arguments and implicitly converts these arguments as necessary. The method also returns the context object, which contains information about the thread’s execution. This ensures that a slot’s receiver is always executed in the context thread. A slot can be a normal class method, a global function, a lambda expression, or a function object.

Invoking a slot is similar to calling a normal member function, but with a few key differences. A slot can receive arguments and return a value, and the result of the slot is returned to the caller using a combiner. The combiner takes the result of a series of slot calls and coalesces them into a single result. In many cases, this result is a simple function of the slot calls, or it may be a container of all the results.