How to share variables among multiple source files in Qt?

In Qt, there are several ways to share variables between multiple source files.

1. Global variables: You can define a global variable in one source file and then use the “extern” keyword to declare and access it in other source files. For example, you can define a global variable “int g_globalVariable = 0;” in one source file and then declare and use it in other source files using “extern int g_globalVariable;”.
2. Singleton pattern: It can be used to create a class that can only be instantiated once, and can contain variables that need to be shared. Other source files can access and modify these variables through an instance of the singleton class.
3. Signal and slot mechanism: This mechanism allows for communication between multiple source files. One source file can pass a variable’s value to another source file by sending a signal, and the receiving source file can then process the variable’s value using a slot function.
4. Shared memory: It is possible to share variables between multiple source files using shared memory. Qt offers the QSharedMemory class to handle shared memory operations, allowing variables to be stored in shared memory and accessed and modified across multiple source files to enable variable sharing.

It is necessary to choose the appropriate method for sharing variables based on specific needs and scenarios. Each method has its own suitable situations and limitations, so the choice should be based on the specific circumstances.