iterate through vector with for loop in c++

Question

I am reading a tutorial about joystick input handling with SDL and I am struggling with a part of the code.

In .h file I got:

std::vector<std::pair<Vector2D*, Vector2D*> > m_joystickValues;

and in .cpp file I got:

m_joystickValues.push_back(std::make_pair(new Vector2D(0,0),new Vector2D(0,0)));

In this case I have one joystick, if there is many joysticks there will more push_backs, I want to access the adresses in "m_joystickValues" so I can delete them in a clean function.

Anyone has an idea how I can do this with a for loop. Thanks

What's stopping your from the good ole' for(int x=0; x<m_joystickValues.size(); x++)? — scohe001
– scohe001, Commented Jul 30, 2014 at 23:07
If possible, change to std::vector<std::pair<Vector2D, Vector2D>> m_joystickValues; to have automatic memory management. — Jarod42
– Jarod42, Commented Jul 30, 2014 at 23:07
Use std::shared_ptr<Vector2D> and std::make_shared<Vector2D>() so there's no need for manual memory management. — David G
– David G, Commented Jul 30, 2014 at 23:22
Which part of writing a for loop are you having trouble with? Have you looked back at your textbook to remind yourself how they work? — Rob Kennedy
– Rob Kennedy, Commented Jul 30, 2014 at 23:24

Vlad from Moscow · Accepted Answer · 2014-07-30 23:18:00Z

4

For example you can use the range-based for statement

for ( auto &p : m_joystickValues )
{
   delete p.first;
   delete p.second;
}

The same can be done using the ordinary for statement

for ( size_t i = 0; i < m_joystickValues.size(); i++ )
{
   delete m_joystickValues[i].first;
   delete m_joystickValues[i].second;
}

Or you can use standard algorithm std::for_each with an appropriate lambda-expression. It is similar to using a for statement with iterators.

edited Jul 30, 2014 at 23:18

answered Jul 30, 2014 at 23:11

Vlad from Moscow

313k27 gold badges204 silver badges358 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jarod42 Over a year ago

The iterator version is missing :-) (with std::vector<std::pair<Vector2D*, Vector2D*>>::iterator instead of auto ^^)

user1597897 · Accepted Answer · 2014-07-30 23:07:27Z

1

for(int i = 0; i < m_joystickValues.size(); i++)
{
    m_joystickValues[i] //do something with this
}

Is this what you are looking for? Also, you could use the at function, since it is more safe.

answered Jul 30, 2014 at 23:07

user1597897

1,5083 gold badges22 silver badges28 bronze badges

Comments

jazaman · Accepted Answer · 2014-07-30 23:15:31Z

1

for(auto& i : m_joystickValues)
{
    delete i.second;
    delete i.first; // or do whatever
}

At end of the loop you can erase the entire vector

m_joystickValues.erase(m_joystickValues.begin(), m_joystickValues.end());

answered Jul 30, 2014 at 23:15

jazaman

1,0194 gold badges12 silver badges30 bronze badges

2 Comments

Jarod42 Over a year ago

You may use m_joystickValues.clear(); instead of erase the whole range

jazaman Over a year ago

@Jarod42 yes that's neater.

Collectives™ on Stack Overflow

iterate through vector with for loop in c++

3 Answers 3

1 Comment

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related