Re: Problem with wring my own iterator

From:

Victor Bazarov <v.bazarov@comcast.invalid>

Newsgroups:

comp.lang.c++

Date:

Mon, 03 May 2010 11:37:49 -0400

Message-ID:

<hrmqkf$l26$1@news.eternal-september.org>

On 5/3/2010 10:58 AM, mast4as wrote:

Hi everyone

I tried to copied the code of some program that uses their own
iterator to loop over some elements of map... The code seems simple
and works in the program I copied it from of course (and I can compile
it) but I can get my own version to work. I get this error message:

xx.cc: In member function ?A::Iterator A::begin()?:
xx.cc:716: error: conversion from
?std::_Rb_tree_iterator<std::pair<const std::basic_string<char,
std::char_traits<char>, std::allocator<char> >, int> >? to non-scalar
type ?A::Iterator? requested
xx.cc: In member function ?int& A::Iterator::value() const?:
xx.cc:737: error: invalid initialization of reference of type ?int&?
from expression of type ?const int?

Could anyone please help me ? Thank you so much -c

class A
{
public:
    A() {}
    typedef std::map<std::string, int> MapStuff;

    class Iterator;

    Iterator begin();
    Iterator end();
    Iterator find( const char *name );

private:

    MapStuff map;
};

class A::Iterator
{
public:
    Iterator();

     Iterator& operator ++ ();

     const std::string& name () const;
     int& value() const;

private:
    //friend class A::ConstIterator;

    A::MapStuff::iterator _i;
};

A::Iterator
A::begin()
{
    return map.begin();

There does not exist a conversion between a map::iterator and your
A::Iterator. Such a conversion is required here. Did you mean to say

_i = map.begin();
return *this;

? Otherwise consider defining a constructor which takes a
'map::iterator' as its argument (by value would be OK, I suppose).

}

A::Iterator::Iterator () : _i()

You default-initialize the contained iterator. What does that do, do
you know?

{
    // empty
}

A::Iterator& A::Iterator::operator ++ ()
{
    ++_i;
    return *this;
}

const std::string& A::Iterator::name () const
{
    return _i->first;
}

int& A::Iterator::value() const
{
    return _i->second;
}

V
--
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