I'm currently studying boost threads. And I came across that the thread class has a constructor that accepts callable objects. What are callable objects?
class CallableClass
{
private:
// Number of iterations
int m_iterations;
public:
// Default constructor
CallableClass()
{
m_iterations=10;
}
// Constructor with number of iterations
CallableClass(int iterations)
{
m_iterations=iterations;
}
// Copy constructor
CallableClass(const CallableClass& source)
{
m_iterations=source.m_iterations;
}
// Destructor
~CallableClass()
{
}
// Assignment operator
CallableClass& operator = (const CallableClass& source)
{
m_iterations=source.m_iterations;
return *this;
}
// Static function called by thread
static void StaticFunction()
{
for (int i=0; i < 10; i++) // Hard-coded upper limit
{
cout<<i<<"Do something in parallel (Static function)."<<endl;
boost::this_thread::yield(); // 'yield' discussed in section 18.6
}
}
// Operator() called by the thread
void operator () ()
{
for (int i=0; i<m_iterations; i++)
{
cout<<i<<" - Do something in parallel (operator() )."<<endl;
boost::this_thread::yield(); // 'yield' discussed in section 18.6
}
}
};
How does this become a callable object? Is it because of the operator overloaded or the constructor or something else?
A callable object is something that can be called like a function, with the syntax object()
or object(args)
; that is, a function pointer, or an object of a class type that overloads operator()
.
The overload of operator()
in your class makes it callable.