CODEWITHSUNDEEP
c++vectorpush-back
Jhenna Foronda
Jhenna Foronda

Reputation: 35

push_back struct into vector

 //prototype    
 void Split(char c, vector <MyString> &outputVector) const           

 //partial code inside split function
 // create new MyString object to push into output vector
 MyString substr;
 substr.mString = newString;
 substr.mLength = size;

 // push new item
 outputVector.push_back(substr);

After I step over the outputVector.push_back() line, the mString data member is not retained. 

//I have two constructors
MyString()
{
    mString = NULL;
    mLength = 0;
}

/*************************************************
 * MyList copy constructor
 * creates a deep copy of a MyString item
 ************************************************/
MyString(const MyString &copy)
{
    mString = new char[copy.mLength];
    int i;

    for(; i < copy.mLength; i++)
    { mString[i] = copy.mString[i]; }

    mString[i] = '\0';
    mLength = copy.mLength;

}

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Upvotes: 0

Views: 780

Answers (4)

Arif Shariar
Arif Shariar

Reputation: 11

I think there are 2 mistakes ,you have done 1.for(i; i < copy.mLength; i++) { mString[i] = copy.mString[i]; } you have to mention ,where the loop will start . 2.mString = new char[copy.mLength + 1]; mString[i] = '\0'; i think ,you got the answer :)

Upvotes: 0

NathanOliver
NathanOliver

Reputation: 180845

You are using an uninitialized variable which is undefined behavior

int i;

for(; i < copy.mLength; i++)

Here we have no idea what i is so anything can be going on but most likely i is larger than copy.mLength so we never enter the for loop. In order to get correct behavior set i to 0 like

int i = 0;

You have another issue with

mString[i] = '\0';

By the time we reach that line i == copy.mLength but the array only has the size of copy.mLength so we are one past the end since arrays are 0 index based. Most likely you need to change your allocation to 

mString = new char[copy.mLength + 1];

to give you space for the null terminator.

Upvotes: 6

Sumeet
Sumeet

Reputation: 779

Correct version of copy constructor

MyString(const MyString &copy)
{
    mString = new char[copy.mLength + 1];
    int i = 0;

    for(; i < copy.mLength; i++)
    { mString[i] = copy.mString[i]; }

    mString[i] = '\0';
    mLength = copy.mLength;

}

Upvotes: -1

Michal Partyka
Michal Partyka

Reputation: 49

http://www.cplusplus.com/reference/vector/vector/push_back/

push_back copies value to vector. Does MyString class have properly defined copy constructor, that copies mString member? I would guess this might be your problem.

Upvotes: 0

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