How do I initialize a const data member?

by

The const variable specifies whether a variable is modifiable or not. The constant value assigned will be used each time the variable is referenced. The value assigned cannot be modified during program execution.

Bjarne Stroustrup’s explanation sums it up briefly:

A class is typically declared in a header file and a header file is typically included into many translation units. However, to avoid complicated linker rules, C++ requires that every object has a unique definition. That rule would be broken if C++ allowed in-class definition of entities that needed to be stored in memory as objects.

A const variable has to be declared within the class, but it cannot be defined in it. We need to define the const variable outside the class.

T1() : t( 100 ){}

Here the assignment t = 100 happens in initializer list, much before the class initilization occurs.

More Related Contents:

  1. Why must const members be initialized in the constructor initializer rather than in its body?
  2. Do the parentheses after the type name make a difference with new?
  3. Does the default constructor initialize built-in types?
  4. How to initialize a const field in constructor?
  5. C++ where to initialize static const
  6. Do I really need to implement user-provided constructor for const objects?
  7. C++: Where to initialize variables in constructor [duplicate]
  8. Why does C++ not have a const constructor?
  9. Has the new C++11 member initialization feature at declaration made initialization lists obsolete?
  10. Different ways of initializing an object in c++
  11. Is there a way to make a C++ struct value-initialize all POD member variables?
  12. What’s the difference between Radio r = Radio(“PSR”, 100.8) and Radio(“PSR”, 100.8)?
  13. Why should I prefer to use member initializer lists?
  14. What is the order of evaluation in a member initializer list?
  15. C++ Member Initializer List
  16. Why isn’t it legal to convert “pointer to pointer to non-const” to a “pointer to pointer to const”
  17. Why is there no call to the constructor? [duplicate]
  18. Do rvalue references to const have any use?
  19. How is a variable at the same address producing 2 different values? [duplicate]
  20. How do I call the base class constructor?
  21. C++ Static member initialization (template fun inside)
  22. Why class data members can’t be initialized by direct initialization syntax?
  23. How can I initialize C++ object member variables in the constructor?
  24. What is the difference between const_iterator and non-const iterator in the C++ STL?
  25. C++ typedef interpretation of const pointers
  26. Modifying a const int in C++ [duplicate]
  27. What destructors are run when the constructor throws an exception?
  28. C++11 anonymous union with non-trivial members
  29. Default and value initialization of POD types in C++
  30. prolonging the lifetime of temporaries

Leave a Comment