Assignment problem

This is a discussion on Assignment problem within the C++ Programming forums, part of the General Programming Boards category; I want to assign a vector to a vector that is returned by a function. Code: #include "Character.h" #include <iostream> ...

  1. #1
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    Assignment problem

    I want to assign a vector to a vector that is returned by a function.


    Code:
    #include "Character.h"
    #include <iostream>
    using namespace std;
    #include <vector>
    
    vector<Character>& makeCharacters() {
    	vector<Character> theParty;
    	bool moreChars, classCorrect;
    	
    	do {
    		string name, clas;
    		cout<<"Enter the name of a character"<<endl;
    		getline(cin, name);
    
    		if(name.empty())
    			moreChars = false;
    		else {
    			moreChars = true;
    
    			do {
    				cout<<"Enter the class of the character"<<endl;
    				getline(cin, clas);
    
    				if(clas.compare("fighter") != 0 && clas.compare("Fighter") != 0 
    				&& clas.compare("mage") != 0 && clas.compare("Mage") != 0
    				&& clas.compare("healer") != 0 && clas.compare("Healer") != 0) 
    				{
    					cout<<"Sorry, that is an invalid class choice."<<endl;
    					cout<<"The choices are Fighter, Mage, and Healer."<<endl;
    					classCorrect = false;
    				}
    				else
    					classCorrect = true;
    
    			} while (!classCorrect);	//END DO WHILE FOR CHAR CLASS
    
    			Character one(name, clas);	//MAKE NEW CHARACTER
    			theParty.push_back(one);
    
    		}	//END ELSE
    
    	} while(moreChars);	//END DO WHILE FOR MORE CHAR
    
    	cout<<"THEPARTYS SIZE: "<<theParty.size()<<endl;
    	return theParty;
    
    }	//END MAKECHARACTERS()
    
    int main() {
    	vector<Character> party;
    	party = makeCharacters();
    	cout<<"PARTYS SIZE: "<<party.size()<<endl;
    	for(unsigned int i=0;i<party.size();i++) 
    		cout<<party.at(i).toString()<<endl;
    	
    }
    Whenever I run it, I make some Characters and theParty's size is increased. But whenever I try to for loop through party, party's size is 0. Is this line wrong?
    Code:
    party = makeCharacters();
    I don't understand why party is being initialized with the vector returned by makeCharacters().

  2. #2
    C++まいる!Cをこわせ! Elysia's Avatar
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    NEVER return a reference to a local variable!
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  3. #3
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    It would be a much better idea to take a reference to a vector as a parameter, and just fill that.

  4. #4
    Or working on it anyways mramazing's Avatar
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    I'm not sure about how to do this with STL but I know you can return static variables because of the static type properties. I have done this before but am not sure about how well this fits in with coding standards. I think that Daved's suggestion is more correct. I would probably call this a hack.

    But here is an example of what I mean.

    Code:
    #define SIZE 16
    char *func(void);
    
    int main()
    {
        char *stuff = malloc(sizeof(char)*SIZE);
        stuff = func();
        printf("%s", stuff);
    }
    
    char *func(void)
    {
        char *p;
        static char thing[SIZE] = "Hello World\n";
        p = thing;
        return p;
    }
    Although in c++ you need to use new and delete instead of free and malloc.

    Here is a good reference to the static variable...
    Static variable - Wikipedia, the free encyclopedia
    -- Will you show me how to c++?

  5. #5
    C++まいる!Cをこわせ! Elysia's Avatar
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    This is BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD!
    You are essentially replacing the pointer with allocated memory with the return value of func, resulting in a memory leak!
    And you don't even release your malloced memory at the end of main!

    You can also get of all this code:
    char *p;
    static char thing[SIZE] = "Hello World\n";
    p = thing;
    return p;
    ...and replace it with...
    static char thing[SIZE] = "Hello World\n";
    return thing;
    Which works the same way, but is shorter.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  6. #6
    Registered User whiteflags's Avatar
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    I agree with Daved.

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