Iterator,container,copy Lost

FFCD · #1 17-Nov-2006, 23:25

I have two questions that im so lost with.

First question is about a copy constructor, how do i makes a copy of the Entry container from the object parameter.

CPP / C++ / C Code:

MediaCatDb::MediaCatDb(const MediaCatDb& mediaCatDb):_entries(NULL)
{
}

and i have two remove functions The first remove function removes based on an Entry object parameter. The object is searched for in the database and removed if found. The second remove function removes an entry from the database referred to by an iterator object.

First remove function

CPP / C++ / C Code:

void MediaCatDb::remove(const Entry& entry)
{
	//ME
	list<Entry>::iterator it;
	
	if ((it = find(_entries.begin(), _entries.end(), entry)) != _entries.end() )
	{
		_entries.remove(entry);
		cout << "Deleted" << endl;
	}
	else
	{
		cout << "Entry not found" << endl  ;
	}

}

am lost on how to do this remove function??

CPP / C++ / C Code:

void MediaCatDb::remove(MediaCatDb::iterator it)
{
		

}

Any comments and help much thanked.

FFCD · #2 22-Nov-2006, 00:15

I have done teh copy constructor is this right??

CPP / C++ / C Code:

MediaCatDb::MediaCatDb(const MediaCatDb& mediaCatDb):_entries(NULL)
{
	_entries = mediaCatDb._entries;

}

amad1337 · #3 22-Nov-2006, 02:23

Quote:

Originally Posted by FFCD

am lost on how to do this remove function??

CPP / C++ / C Code:

void MediaCatDb::remove(MediaCatDb::iterator it)
{
         MediaCatDb::iterator tmp;
	//This will call the copy constructor
	MediaCatDb db =  *it;
	

	if ((tmp = find(_entries.begin(), _entries.end(), db)) != _entries.end() )
	{
		_entries.remove(db);
		cout << "Deleted" << endl;
	}
	else
	{
		cout << "Entry not found" << endl  ;
	}	

}

Your copy constructor is seem to be right.

FFCD · #4 22-Nov-2006, 03:33

Thank you,

FFCD · #5 22-Nov-2006, 03:51

I dont think that worked because i keep on getting errors say that " error C2440: 'initializing' : cannot convert from 'Entry' to 'MediaCatDb'
1> No constructor could take the source type, or constructor overload resolution was ambiguous " and " error C2664: 'std::list<_Ty>::remove' : cannot convert parameter 1 from 'MediaCatDb' to 'const Entry &'
1> with
1> [
1> _Ty=Entry
1> ]
1> Reason: cannot convert from 'MediaCatDb' to 'const Entry'
1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called " do you know what this could mean??
Thanks

amad1337 · #6 22-Nov-2006, 04:59

Sorry i wasn't awake

try this one

CPP / C++ / C Code:

void MediaCatDb::remove(list<Entry>::iterator it)
{
        
	

	if ((it = find(_entries.begin(), _entries.end(), it)) != _entries.end() )
	{
		_entries.remove(*it);
		cout << "Deleted" << endl;
	}
	else
	{
		cout << "Entry not found" << endl  ;
	}	

}

Just a remark: if you already have i member function looking like the one under here you
dont need the above if you call the member function under here with argument like remove(*it). This will cause
*it implicitly to convet to Entry reference object.

CPP / C++ / C Code:

void MediaCatDb::remove(const Entry& entry)
{
	//ME
	list<Entry>::iterator it;
	
	if ((it = find(_entries.begin(), _entries.end(), entry)) != _entries.end() )
	{
		_entries.remove(entry);
		cout << "Deleted" << endl;
	}
	else
	{
		cout << "Entry not found" << endl  ;
	}

}

FFCD · #7 23-Nov-2006, 06:48

It still not working error : " no operator found which takes a right-hand operand of type 'const std::list<_Ty>::_Iterator<_Secure_validation>' (or there is no acceptable conversion)
1> with
1> [
1> _Ty=Entry,
1> _Secure_validation=true
1> ]"

my code

Code:

MediaCatDb::MediaCatDb(){}


MediaCatDb::MediaCatDb(const MediaCatDb& db):_entries(NULL)
{
	_entries = db._entries;

}
void MediaCatDb::add(const Entry& entry)
{
	
	list<Entry>::iterator it;
	
	if ((it = find(_entries.begin(), _entries.end(), entry)) != _entries.end() )
	{
		cout << "Entry present" << endl;
	}
	else
	{
		_entries.push_back(entry);
	}
	
}
void MediaCatDb::remove(const Entry& entry)
{
	
	list<Entry>::iterator it;
	
	if ((it = find(_entries.begin(), _entries.end(), entry)) != _entries.end() )
	{
		_entries.remove(entry);
		cout << "Deleted" << endl;
	}
	else
	{
		cout << "Entry not found" << endl;
	}
	
}
void MediaCatDb::remove(list<Entry>::iterator it)
{
	
	if ((it = find(_entries.begin(), _entries.end(), it)) != _entries.end() )
	{
		_entries.remove(*it);
		cout << "Deleted" << endl;
	}
	else
	{
		cout << "Entry not found" << endl  ;
	}	
	
}
MediaCatDb::iterator MediaCatDb::begin()
{
	return iterator(_entries.begin());	
}
MediaCatDb::const_iterator MediaCatDb::begin() const
{
	return const_iterator(_entries.begin());
}
MediaCatDb::iterator MediaCatDb::end()
{
	return iterator(_entries.end());
}
MediaCatDb::const_iterator MediaCatDb::end() const
{
	return const_iterator(_entries.end());
}

in the header file the following is declared

Code:

class MediaCatDb
{
	typedef list<Entry> Container;
	Container _entries;

public:
	typedef Container::iterator iterator;
	typedef Container::const_iterator const_iterator;

FFCD · #8 28-Nov-2006, 17:47

Sloved my prob throught out was nto using this

Container::iterator it = _entries.begin();

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Iterator,container,copy Lost

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