The Vector Class

• I need the vector class for testing and other things.
  • So we will look at it now.
• Read 631 - 653
  • If you run across syntax you do no know ASK
• Look at the vector reference on cplusplus.com
• The vector is an element of the C++ standard library
  • It is a container, it holds a collection of homogenious objects.
  • It can hold any type of object however.
  • It support many functions.
  • It supports iterators.
• A vector is a dynamic array
  • The size does not need to be known at runtime.
  • As you add elements, the vector will grow to the size needed.
  • As you delete elements, the vector may shrink.
• We implmented the foundation of a vector last semester.
  • It has a pointer to an "array" of memory
  • You keep track of a size the number of elements and a capacity which is the size of the block of mememory
  • When size = capacity, allocate new memory.
• Vectors are implmented as templates
  • This allows us to declare a vector of almost anything.
• Basics
  • You must include vector

    • #include <vector> 

  • Vector is part of namespace std

    • // choice 1
      using namespace std;
      
      vector< ...> 
      // or choice 2
      std::vector<...> 

    • The second is a must in header files.
• Declaring Vectors

  • vector <dataType> identifier;
    vector <dataType> identifier(size);
    vector <dataType> identifier(size, value);
    vector <dataType> identifier({initializer list});
    vector <dataType> identifier = {initializer list}; 

• Examples

  • vector <int> myNumbers;
    vector <CritterT> monsters;
    vector <RoomT *> rooms; 

• You can append to the vector with push_back(item).
• The [] operators work just fine.
• size() returns the size of the vector.
• pop_back() removes the last item.
• auto and auto &