Advanced Classes

• Static methods.
  • Static allows you to create a member that is shared across all instances of a class.
  • We will focus on static member functions for now.
  • These member functions do not have a this pointer.
  • But they can access protected and private members if they are passed to the function.
  • You can call them without creating an instance of the class.
• Static Data
  • Again, this is a value shared across all members of a class.
  • You need to declare the variable outside the class before c++17
    • This is usually done in the implementation file.
    • Lifetime for static data is from when it is declared to the end of the program.
    • This is essentially a global variable in the namespace of the class.
  • In c++17 and beyond you can declare a variable to be static inline
  • This allocates the space automatically.
• You can declare member data to be const as well
  • But it must be initialized in c_tor initializer or in class initializers
• We have discussed const members in the past
  • Static members can not be const.
  • But this makes sense as they don't have any data to change.
  • Your author is a big fan of declaring a function const when it is.
• Please see staticDemo.cpp
• Mutable members
  • If you have member data that might change in a const method
    • For example record keeping, how many times has the cell been accessed in a spreadsheet.
    • Or perhaps the current pointer in the DLCL class
  • They can be marked mutable and thus changed in const functions.