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Print value from constructor
#include<iostream>
using namespace std;
class Book{
public:
string title;
string author;
int pages;
Book(string aTitle, string aAuthor, int aPages){
aTitle = title;
aAuthor = author;
aPages = pages;
}
};
int main(){
Book book1("Harry","JK",500);
Book book2("Lord","Tolkein",450);
cout << "Title : " << book1.title << "; Author : " << book1.author << "; Pages : " << book1.pages;
return 0;
}
This outputs
Title : ; Author : ; Pages : 404155672%
The output I expected :
Title : Harry; Author : JK; Pages : 500;
I had tried to get the same output using printf also.
printf("Title : %s",book1.title);
This only outputs,
Title : ;
String from constructor doesn't show properly. Even, in first code Integer had converted to hexadecimal.
1 answer
That's because of this part of the code:
Book(string aTitle, string aAuthor, int aPages){
aTitle = title;
aAuthor = author;
aPages = pages;
}
You're attibuting the properties from the class to the function parameter values. As the properties aren't initialized yet, they're getting just random values. It should have been the oposite. Like this:
Book(string aTitle, string aAuthor, int aPages) {
title = aTitle;
author = aAuthor;
pages = aPages;
}
you can also use member initializer syntax:
Book(string aTitle, string aAuthor, int aPages) : title(aTitle), author(aAuthor), pages(aPages) {
}
or like this:
Book(string aTitle, string aAuthor, int aPages) : title{aTitle}, author{aAuthor}, pages{aPages} {
}
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