CODEWITHSUNDEEP
c++vectoriterator
jmasterx
jmasterx

Reputation: 54103

Iterator for vector of pointers not dereferencing correctly

Here is my issue:

I have a std::vector<AguiWidgetBase*> which is used to keep track of child controls.

I have these two functions to return iterators:

std::vector<AguiWidgetBase*>::const_iterator AguiWidgetBase::getChildBeginIterator() const
{
    return children.begin();
}

std::vector<AguiWidgetBase*>::const_iterator AguiWidgetBase::getChildEndIterator() const
{
    return children.end();
}

I then use it like this:

for(std::vector<AguiWidgetBase*>::const_iterator it = box->getChildBeginIterator(); 
    it != box->getChildEndIterator(); ++it)
{
    it->setText("Hello World");
}

and I get these errors:

Error   3   error C2039: 'setText' : is not a member of 'std::_Vector_const_iterator<_Ty,_Alloc>'   c:\users\josh\documents\visual studio 2008\projects\agui\alleg_5\main.cpp   112
Error   2   error C2839: invalid return type 'AguiWidgetBase *const *' for overloaded 'operator ->' c:\users\josh\documents\visual studio 2008\projects\agui\alleg_5\main.cpp   112

Why is it giving me these errors?

Thanks

Upvotes: 7

Views: 11277

Answers (3)

Peter
Peter

Reputation: 7324

As others have noted, this is because the objects stored in your vector are pointers, so you have an extra level of indirection to the actual objects.

You may be able to use a boost::ptr_vector to collect the AguiWidgets by pointer but work with them as though they're stored by value? I haven't used it extensively but my vague recollection is that it works that way.

Upvotes: 0

TheUndeadFish
TheUndeadFish

Reputation: 8171

Is there a way I can change my iterators so that it-> works?

Not directly, but you could do something like:

for(std::vector<AguiWidgetBase*>::const_iterator it = box->getChildBeginIterator(); 
    it != box->getChildEndIterator(); ++it)
{
    AguiWidgetBase* p = *it;

    p->setText("Hello World");
}

Upvotes: 5

GManNickG
GManNickG

Reputation: 503805

Because an iterator acts like a pointer, and in this case a pointer to a pointer.

You'd need:

(*it)->setText("Hello World"); // dereference iterator, dereference pointer

Upvotes: 24

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