Why should use another constructor in that case?

Question

1.00/5 (1 vote)

See more:

Rectangle(float a):Shape(a) {};  //!3! Missing Constructor

why we need this??

What I have tried:

#include<iostream>
using namespace std;
class Shape
{
public:                     //!1! Constructor must be public!
	Shape(float a)
	{
		w = a;
	}
	void get()              //!2! Member hast to be public
	{
		cin >> w >> h;
	}
protected:
	float w, h;
};

class Rectangle : public Shape
{
public:
	Rectangle(float a):Shape(a) {};  //!3! Missing Constructor
// protected:                   //!4! Member hast to be public
	void area()                 //!5! missing brackets
	{
		cout << w*h << endl;
	}
};

int main()
{
	Rectangle R(1.0);     //!6! spelling wrong + constructor mismatch
	R.get();
	R.area();
	return 0;
}

Posted 9-Aug-22 2:22am

Member 15653662

Updated 9-Aug-22 6:25am

Add a Solution

Comments

Richard Deeming 9-Aug-22 8:44am

Because you do.

Seriously, an unexplained code-dump, some cryptic comments, and a single line of "why we need this?" does not make for a good question.

If you want a proper answer, click the green "Improve question" link and update your question to include a clear and complete description of the problem you are trying to solve, what you have tried, and where you are stuck.

Richard MacCutchan 9-Aug-22 11:52am

The posted c ode works correctly. So none of the comments are valid.

merano99 9-Aug-22 12:12pm

He copied my answer to a question and the comments mark where it was wrong before. Apparently he copied without understanding it.

Richard MacCutchan 9-Aug-22 12:29pm

Sadly not an unusual event.

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Answer 1 · 2022-08-09T03:06:00

Solution 1

If I copy and paste your code into an online compiler - onlinegdb.com - it compiles with no errors, and runs. It doesn't tell the user what to input, or even that he should input anything, but it works: I give it "2.6 4.8" and it gives me "12.48".

So what is the problem? At a guess, your teacher has added comments saying what he doesn't like, and you have fixed some of them. Which ones you think you have fixed, we have no idea ...

Posted 9-Aug-22 3:06am

OriginalGriff

Comments

merano99 9-Aug-22 12:14pm

The problem seems to be that he does not understand the code he copied from my answer. It really would have been better if I had left out the mistakes and just commented on what didn't fit. Unfortunately, he didn't correct anything himself, not even the typos.

merano99 · Answer 2 · 2022-08-09T06:25:00

We had the code commented on 1-Aug-22 in response to N Hasan's question.

Quote:
Need to explain all the cases according to the errors

https://www.codeproject.com/Answers/5338717/Need-to-explain-all-the-cases-according-to-the-err#answer2

It's amazing how little personal effort goes into this question.

//Edit:
I can briefly touch on the basic context. However, it would be clearly necessary to read this in a basic book.

The Rectangle class inherits from the Shape class. The data is protected and is neither inherited nor is it directly modifiable via the Rectangle class. The class Shape has only one constructor, which has a float parameter. So the parameter is needed when creating an instance of the class.

C++

class Shape {
public: 
	Shape(float a);
	...
protected:
	float w, h;
};

class Rectangle : public Shape

If you want to create an instance of the class Rectangle, the constructor of Shape is called, too. Now there are some questions.
1. where does the constructor of Shape get the parameter?
2. how are the protected parameters initialized?

In initialization lists, inherited properties cannot be accessed, therefore the properties are initialized by calling the corresponding constructor of the parent class.