Need help with containers
Author
public void draw_all_vec(vector<int> const vec)
{
for(int x = 0; x <vec.size();++x)
{
cout vec[x];
}
}
How i would i generalise this for all types of containers not just vectors. Would i need to use a template method, if so how would you use a template method to generalise a container.
You would do something like:
template <typename Container>void draw_all(const Container & container) { for (typename Container::iterator itr = container.begin(); itr != container.end(); ++itr) { // draw with *itr }}
Do you want to be able to 'draw' any object type or is there a subset of objects that should be drawable?
Have you considered using a base drawable class with a pure virtual draw function. Then anything that must be drawable can inherit from this class and define a function that tells the system how to draw it?
Then you can have pointers to all your drawable objects and simply loop through them and call the draw function.
Have you considered using a base drawable class with a pure virtual draw function. Then anything that must be drawable can inherit from this class and define a function that tells the system how to draw it?
Then you can have pointers to all your drawable objects and simply loop through them and call the draw function.
template <typename Container>void draw_all(const Container & container) { for (typename Container::iterator itr = container.begin(); itr != container.end(); ++itr) { // draw with *itr }}This could be written a llittle better as:
template <typename Container>void draw_all(const Container & container) { typename Container::iterator iter, begin, end; begin = container.begin(); end = container.end(); for (itr = begin; itr != end(); ++itr) { // draw with *itr }}You could even use const_iterator if you know that you are not changing the state of the object contained.
ace
Another option is to accept a pair of iterators. This complicates the interface a bit, in exchange for the ability to output ranges of a container (rather than always having to use the whole thing).
This can also be done with std::algorithms:
template <typename InputIterator>void draw_all(const InputIterator& begin, const InputIterator& end) { for (InputIterator it = begin; it != end; ++it) { // draw with *itr }}//...draw_all(myVector.begin(), myVector.end());draw_all(myMap.find("foo"), myMap.find("quux"));// Actually, because the map iterators will be iterators over key/value pairs// and you presumably want to 'draw with' just the value, you will probably// need a specialization in that case :/This can also be done with std::algorithms:
#include <algorithm>using namespace std;struct draw { void operator() (const Thing& t) { thing.draw(); // invoke Thing::draw() const }};// ...Vector<Thing> myVector;// ...// Create a draw object; the for_each will invoke its operator() with each// item in the range.for_each(myVector.begin(), myVector.end(), draw());// Or if we just want to output Things using // operator<< (ostream&, const Thing&):copy(myVector.begin(), myVector.end(), ostream_iterator<Thing>(cout, ""));// The "" can be any string literal; it is used as a separator between// output items.This topic is closed to new replies.
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