Requesting data from a vector with a struct?

Code:

---

    struct data
    {
          string name;
          string title;
          string author;
    };


    vector<data> books;

---

When you have stored data inside a vector like that, how would you request all the names, titles and authors inside the vector, using cout?

use an iterator

Or use a loop.

Code:

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for(int i = 0; i < books.size(); i++){
    std::cout<<books[i].name;
    //ETC
}//for

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Quote:

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Originally Posted by prog-bman

Or use a loop.

Code:

---

for(int i = 0; i < books.size(); i++){
    std::cout<<books[i].name;
    //ETC
}//for

---

---

Thanks!

Quote:

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Originally Posted by BigFish21

use an iterator

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Is it better than a loop? How do you use it in the example?

I wouldn't say it's better - in fact, I'd say it's disadvantageous when you can use indexes.
You would use an iterator like this:

Code:

---

for(std::vector<data>::iterator i = books.begin(); i != books.end();)
{
    std::cout << *i++;
}

---

Iterators become invalidated (invalid) if you perform certain operations on the container, such as resizing buffer or capacity.
Indexes never become invalid.

Quote:

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Is it better than a loop?

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A loop is a control structure. An iterator is an object. In this case, the comparison is between using an index with a loop (prog-bman's example) or an iterator with a loop. It is also possible to use iterators with generic algorithms, but ignore that for now if you have not yet reached that stage in your learning.

Quote:

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How do you use it in the example?

---

Code:

---

for (vector<data>::const_iterator i = books.begin(), end = books.end();
    i != end; ++i)
{
    std::cout << i->name; // etc
}

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Note that prog-bman's example is slightly inaccurate since the index is not of type int, but of type vector<data>::size_type, which is typically an unsigned int.

Quote:

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Originally Posted by Elysia

Indexes never become invalid.

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That is not true: indices can become invalid when the container shrinks.

Fine, fine

Code:

---

for(std::vector<data>::size_type i = 0; i < books.size(); i++){
}//for

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;)

Quote:

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Originally Posted by laserlight

That is not true: indices can become invalid when the container shrinks.

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Ah true, true. I never thought of that one.
Nevertheless, an iterator will also become invalid if the container shrinks beyond its position.
Iterators are a good idea, but the fact that they become invalid makes their usefulness drop. Thankfully, I have solved that issue in my own iterators.

Quote:

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Iterators are a good idea, but the fact that they become invalid makes their usefulness drop.

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I would say that it just makes them slightly more complicated to use.

I suppose you could see it that way, too.