Skip to main content

Advanced C++ - Conversion constructor and operator

When we are defining class we sometimes would like to allow easily convert that class from and to previously defined-type objects (ex. int). We can do that using conversion constructor and conversion operator:
  • conversion constructor - it is constructor which has one parameter - type which constructor should allow to convert from. It allows to convert previously defined object of type as in constructor paramter into object of class where constructor belongs to
  • conversion operator - it is overloaded operator type() - where type is type of object which we can convert this class object into
Let's see below example for better understanding:
Output of this example is:
In that example in our class TestClass we are defining two conversion constructors.
  • conversion constructor for type int (point I)
  • conversion constructor for type string (point II)
Next in main function we are invoking that constructors converting int and string types to our class TestClass type (point V and VI - see first two lines of output).
In point III and IV we are defining two conversion operator (into type int and string). As you can see in points VII and VIII, those conversion operators allows us convert object of TestClass to object of int or string.
Now take a look at points IX and X. We you uncommet it you will receive compiler error. It is because we have defined neither conversion constructor nor conversion operator for type char*.
I hope you understood how to define and how to use conversion constructor and conversion operator.

If you have any questions or suggestions, write in comments, please.

Code for this example you can find and download here:
https://github.com/xmementoit/CppAdventureExamples/tree/master/advancedCpp/conversionConstructorAndOperatorhttps://github.com/xmementoit/CppAdventureExamples/tree/master/advancedCpp/conversionConstructorAndOperator
Labels:

Comments

  1. cpp_engineer3 October 2013 at 09:22

    Nice article thanks for that information.

    ReplyDelete

Post a Comment

Popular posts from this blog

GDB Automatic Deadlock Detector

Have you ever had a problem with detection deadlock between threads in your C/C++ application? Would you like to do that automatically? Try this GDB Automatic Deadlock Detector from my github: GDB Automatic Deadlock Detector Picture source: http://csunplugged.org/wp-content/uploads/2015/03/deadlock.jpg1286488735
Post a Comment
Read more

STL - count and count_if algorithms

One of the basic and most useful STL algorithms is algorithm which can be used to count number of elements within selected container according to specified criteria. In order to do that we can use std::count or std::count_if algorithm. std::count (firstElementIterator, lastElementIterator, elementForSearch) - is function which will go through container using firstElementIterator and lastElementIterator and return number of container elements which value is equal elementForSearch std::count_if (firstElementIterator, lastElementIterator, UnaryPredicateFunction) - is function which examine range from firstElementIterator to lastElementIterator and return number of container elements which fulfill UnaryPredicateFunction criteria. UnaryPredicateFunction is function having following signature: bool functionName(const Type& a) . So, count_if returns number of elements where UnaryPredicateFunction returns true for. For better understanding let's take a
Post a Comment
Read more

Advanced C++ - Stack unwinding

Stack unwinding is normally a concept of removing function entries from call stack (also known as Execution stack, Control stack, Function stack or Run-time stack). Call Stack is a stack data structure that stores active functions' addresses and helps in supporting function call/return mechanism. Every time when a function is called, an entry is made into Call stack which contains the return address of the calling function where the control needs to return after the execution of called function. This entry is called by various names like stack frame , activation frame or activation record. With respect to exception handling , stack Unwinding is a process of linearly searching function call stack to reach exception handler. When an exception occurs, if it is not handled in current function where it is thrown, the function Call Stack is unwound until the control reaches try block and then passes to catch block at the end of try block to handle exception. Also, in this proc
Post a Comment
Read more