CODEWITHSUNDEEP
c++stringfunctionstruct
Adeel Anwar
Adeel Anwar

Reputation: 799

Why does my struct only store string on the last one and not every?

So I made a struct and I called it inside a function but things are not going well...

the struct is as follows...

STRUCT FUNCTION

struct Line {
  private:
    int lineNumber;
    char lineString[];
  public:
    bool set(int n,const char* str);
    void display() const;
};

Everything is working within the function just fine, I store the lineN and lineS then send them off to the function called... bool set(int n, const char* str); (from above) using a struct named storage. After the first while loop, I used a function named display to...display lol.

SET FUNCTION

void List::set(int no){
Line storage[no];
    int i =0, x;
    while (i!=no){
        cout << "Enter line number : ";
        cin  >> lineN;
        cout << "Enter line string : ";
        cin  >> lineS;
        x = storage[i].set(lineN, lineS);
        if (x == 1){
            i++;
    }
}
i=0;
while (i!=no){
    storage[i].display();
    i++;
    }
}

Besides checking for "true / false", True being any positive integer, False being 0 or negatives integers. I am using the following bool to store numbers (if they are true) inside the storage struct... I think the problem lies here but I cant seem to wrap my head around it...

BOOL FUNCTION

bool Line::set(int n, const char* str){
    int i;
    if (n >= 1){
        lineNumber = n;
        for (i=0;i<6;i++){
            lineString[i]=str[i];
        }
        lineString[6]='\0';
        return true;
    }
else if (n <= 0)
    return false;
}

DISPLAY FUNCTION

void Line::display()const{
cout << "LINE: " << lineNumber << " STRING: " << lineString << endl;
}

however, when I hit run the program and lets say I enter 3 times... line number and line string... my result come out as follows...

INPUT: 

Enter line number : 3
Enter line string : ABCDEF
Enter line number : 6
Enter line string : YYUTXL
Enter line number : 8
Enter line string : XYXYXX

OUTPUT: 

LINE: 3 STRING: 
LINE: 6 STRING: 
LINE: 8 STRING: XYXYXX

So my question is why is not being stored inside string prior to the last one, if i do this 2 times, only the second one/last one will have strings inside it. I am storing it correctly am I not?

OUTPUT I HOPED FOR: 

LINE: 3 STRING: ABCDEF
LINE: 6 STRING: YYUTXL
LINE: 8 STRING: XYXYXX

Upvotes: 0

Views: 556

Answers (1)

user1342784
user1342784

Reputation:

The trouble is that this is creating an empty array:

char lineString[];

You are not telling it how big to make it, so it is making it zero bytes long. Thus, your attempt to save a six character string is overwriting memory.

You really should use std::string, but if you don't want to, you at least need to say how big your string is:

char lineString[50]; // save up to 49 characters + NULL.

Upvotes: 5

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