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Programming-Idioms

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  • Dart

Idiom #271 Test for type extension

If a variable x passed to procedure tst is of type foo, print "Same type." If it is of a type that extends foo, print "Extends type." If it is neither, print "Not related."

tst(x) {
  if (x.runtimeType == Foo) {
    print("Same Type.");
  } else if (x is Foo) {
    print("Extends type.");
  } else {
    print("Not related.");
  }
}

Warning: One can create a class that override its runtimeType property,
#include <iostream>
#include <type_traits>
template<typename T>
void tst(T)
{
    using namespace std;

    // Strip away any references and pointer
    typedef remove_const<remove_pointer<decay<T>::type>::type>::type D;

    if(is_same<D, foo>::value)
    {
        cout << "same type" << endl;
    }
    else if(is_base_of<foo, D>::value)
    {
        cout << "extends type" << endl;
    }
    else
    {
        cout << "not related" << endl;
    }
}

New implementation...
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tkoenig