Skip to main content

7. Static members, this, references, const

23/02/23

this & static methods​

this​

  • An object is a collection of data (its state)
  • For functions to actually do something to an object, they need to know which object to affect.
  • (Non-static) member functions have an implicit extra parameter saying which object to act on.
    • Parameter type is a pointer to object
    • And the parameter name is this

Static methods​

  • static members are shared between all objects of that class
  • NOT associated with a specific object
  • Static member functions do not have a this pointer

References​

  • References give a new name to an existing item
  • Look like normal variables
  • Act like pointers.
  • References are labelled with an &

Passing Parameters​

  • When a function is called, the values of the parameters are copied into the stack frame for the new function
  • Functions get a copy of the variable

References vs pointers​

  • Pointers can be made to point to something else
  • References always bind to a single object at creation, cannot be bounded to a new object
  • References always have to refer to something, must give them a thing to refer to on initialisation. No such thing as NULL reference
  • Pointers need * or -> to deference them, to access the thing pointed to
  • Java object references act like C/C++ pointers, NOT C++ references

Uses​

  • Need to keep same syntax.
  • Useful as return values, to chain functions together.
  • References are necessary for operator overloading

const​

  • const cannot be changed
  • The thing pointer at through a pointer to const cannot be changed using the pointer. (const before *)
  • Can also prevent the pointer itself from being changed (const after *)