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STL vector

Started by MagTDK May 22, 2002 at 6:11 PM 6 replies 250+ views

Original Post

May 22, 2002 at 6:11 PM

How do I test if an STL vector contains nothing? I have a function that needs to test if an element already exists in my vector. The problem is, there''s nothing in it the first time through so I get an error. Here is some source:

  
// This is declared in my class header

std::vector<CTexture> STLVector;

void CTexture::Load (std::string file)
{

	std::vector<CTexture>::iterator Iterator;

	for (Iterator = STLVector.begin(); Iterator != STLVector.end(); Iterator++) {

		// Test if element exists and if it does, return from this function


	}

	// Otherwise continue

	CTexture Temp;

	Temp.filename = file;
	
	STLVector.push_back(Temp);

}

Bloodshot Eye

May 22, 2002 at 6:34 PM

STLVector.empty() will tell you if the vector is empty. Though I''m not an expert I would have thought that if the vector was empty then STLVector.begin() would return STLVector.end() and your loop should exit right away.

Cheers,

Ryan.

DerekSaw

May 22, 2002 at 7:23 PM

Another thing... it is a little faster to use ++Iterator than of Iterator++.

[edited by - DerekSaw on May 22, 2002 8:25:13 PM]

MagTDK

May 22, 2002 at 8:02 PM

I''ve never used the find keyword, what library does it belong too?

I''m getting this error: ''find'' : undeclared identifier

Fruny

May 22, 2002 at 8:04 PM

Shannon Barber

May 22, 2002 at 8:13 PM

find is NOT a keyword

Bloodshot Eye

May 23, 2002 at 5:24 AM

MagTDK, I don''t think you''ve been given the full story on find. If you use find with your vector of CTexture then its going to be using the == operator to compare each element with the third argument you pass to find, which in this case is going to be the file parameter to your Load member function. i.e.

find(STLVector.begin(), STLVector.end(), file);

The problem with this is that comparing a CTexture to a string wont go down well with your compiler. To fix that your going to need to write an operator== member function for your CTexture class.

Something like this:

  
bool CTexture::operator==(const std::string& fileName) const
{
    return texFile == fileName;
}

Were texFile is the file name member of the CTexture class.

Cheers,

Ryan.

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