Redefinition of class c как исправить

The redefinition of class C++ header files error happens when developers redefine the same class with identical values and commands. As a result, the inputs confuse the system because proper multiple redefinition C++ operations must have different properties and elements.

Therefore, our experts wrote this comprehensive guide explaining the redefinition of function C++ using simple examples and discussing the most common culprits that recreate the error.

So, less experienced developers and programmers should be fine with debugging the C++ error redefinition of function error from their syntax because this article answers your questions.

Why Redefinition of Class C++ Is Invalid? 3 Common Reasons

The redefinition of class C++ inheritance error is invalid because programmers usually redefine the same class with identical commands and values. Therefore, the system does not understand the difference between both scripts, launching the redefinition of variable C++ mistakes in several code lines.

Furthermore, developers can also experience this error when writing a class in multiple files, causing a few mistakes due to repeated actions. For instance, the redefinition constructor C++ prompt must have unique values and tags because the system identifies its changes.

As a result, many programmers reported the same error when defining classes in header files. This inconvenience happens because the program drags the primary definition into a translation unit by the header file.

On the flip side, the in include file redefinition of the second message keeps the original structure that blocks further operations. In addition, the invalid message has several forms, so our experts recommend learning about the most common one.

The following example provides the typical error script:

However, learning the error’s possible culprits and syntaxes is essential when debugging the mistake from your system. Therefore, we created two chapters that recreate the error, including different elements and commands. In addition, we will show you the debugging syntaxes after.

– Using the Game Object Command

The redefinition of class error in C++ almost always happens when developers introduce the game object command without fair values. In addition, less experienced users must know this error can affect straightforward syntaxes unless they link the values correctly.

As a result, the solutions methods will not change, although your document will have different inputs. However, we will not provide the solutions in this section.

First, read the following example for the code’s first part:

As you can tell, introducing game objects is not complicated because the values are similar. However, this is only the code’s initial part because another game object command launches the error.

Although the second code has fewer values and elements, it confuses the system because the developer redefines the same header class.

The following example shows the second part:

The implementation of the CPP files is incorrect in these scripts because the system cannot link their commands and values.

Furthermore, several changes in the code are vital to helping developers and programs enable the system’s functions. First, however, let us discover why the error appears when introducing ratios.

– Writing Ratios in Multiple Files

Developers will face the same error when writing ratios in multiple files with identical values. Again, we will show you two syntaxes because the full script has several commands and documents.

Although the ratios are similar to the game object, a few prompts differ. Fortunately, debugging the error is not complicated, but let us first provide the invalid values.

Learn more about the primary code in the following example:

Although the constructors and numerators have fair values, the complete syntax must have the header file with the ratio commands. You can learn about this syntax in the following example:

Unfortunately, the second syntax cannot handle the redefinition of the same class in C++, halting further operations and changes. Therefore, it is time to discover the debugging methods that resolve the error.

Fixing the Redefinition of Class in C++: 2 Full-proof Methods

To fix the redefinition of class in C++, you should correctly define the class in both scripts. If that doesn’t fix the error, you will have to fix the value of ratios. Meanwhile, you must not determine the style for a second time for enabling function and initiating operation.

Learn how to change the script by looking at the following code:

As you can see, the solution is not complicated, but developers must change all elements and tags that cause the error. In addition, the next example implements the CPP files with proper forms, so keep reading for more:

This is everything developers, and programmers need to remove the annoying error by fixing the redefinitions. So now, let us discover the second option.

– Correcting the Ratios

Correcting the ratios and their values is an excellent way of debugging the syntax without affecting the rest of the document. For instance, not redefining the ratio will prevent the system from displaying errors.

Developers can use the following example for more:

Furthermore, our experts suggest introducing an output stream, so this command might be essential, as shown here:

Both examples correct the ratios and fix the bug in your system. So, developers must not change the primary and CPP files to remove the error message.

Conclusion

Creating complex documents and operations in C++ is only sometimes straightforward, as confirmed by this annoying error message. Fortunately, our guide explained many vital aspects, including the following bullet points:

• Redefining classes in C++ is not essential with multiple scripts and files
• Our experts suggest checking the primary and secondary functions before linking the commands
• Programmers can experience this error when they redefine the same class with identical values and elements
• Several programmers reported the same error when creating ratios for various purposes and with different inputs
• Debugging the error will not cause other mistakes in your document

This ultimate programmer guide is everything users need to learn how to redefine a class in C++ correctly. As a result, you will create full-proof projects and programs that no errors can harm.

Recommended Answers

All 16 Replies

#ifndef MYHEADER_H
#include MYHEADER_H

// declare class and other stuff here

#endif

class player
{
    public: int money;
    int roll;
    int spotID;
    private:
    char name[45];
    bool banker;
    void getOriginalValues()
    {

    }
};
player p1,p2,p3,p4,p5,p6;

#ifndef PLAYER_H
#define PLAYER_H

class player
{
    public: int money;
    int roll;
    int spotID;
    private:
    char name[45];
    bool banker;
    void getOriginalValues()
    {

    }
};
player p1,p2,p3,p4,p5,p6;

#endif

#pragma once

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Single class has a Class Redefinition Error

I’m new to C++, and I’m having a problem with my class definitions in a header file. The code for the header file (Student.h) is:

4 Answers 4

You need header guards on that header file. It is presumably being included twice.

Modify the header, adding these lines to the beginning and end.

With these directives added, the compiler will ignore all contents of the header file if it has already been parsed.

Alternatively, while it is not standard C++, all major compilers will allow you to put a single

as the first line of the header to prevent it from being parsed multiple times.

as the first line of a header file, instead of the defines. Even if this is non-standard, it does avoid name clashes and can reduce compile time.

See the Wikipedia entry on include guards for a more extensive explanation of the problem and information on how to avoid it.

In short, there are two ways to do it

Version 1, #defined include guards

Usually the #define is called some variation of the file name since it has to be different in every include file.

Version 2, #pragma once

This pragma is (as most pragmas) not portable to all compilers, but some of the most important ones. It also has the advantage of not needing a manually assigned name.

Which you use is up to you, but you most likely have to pick one 🙂

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C++ compile error: redefinition of ‘class::class’

I have added the errors within comment lines of the code for the highlighted lines by the compiler.

NOTE: #endif exists at the end of header file

All of the most popular questions about this error concluded that header guards were needed, although, there are guards already included in this code. I thought I was misunderstanding how to properly separate the initialization list between header and source files but when I commented that out it was still producing the same error.

2 Answers 2

Basically, it should look like this in your header:

You are getting redefinition errors ( which i think are linker errors, and not compile errors ) because Address::Address() and Address::Address(const string&, const string&, const string&, const string&, const string&) are already defined in the header file, and you define them again in the CPP file

To avoid that, you need to replace function definition by declarations in your header file, by replacing <> by ; in your header file, this way :

At the exception of inline and template functions, function declaration goes in header file, and definitions goes into the CPP file

Not the answer you’re looking for? Browse other questions tagged c++ class header-files or ask your own question.

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C++ Error message redefinition of functions

I am using two stacks to implement a queue class. My header file looks like:

And my cpp (implementation) file looks like:

(other functions omitted).

However, using Xcode 4.5, it keeps saying that my functions (MyQueue,

MyQueue, enqueue, peek, etc.) are redefined. Can anyone help me to clarify where have I redefined them?

4 Answers 4

You’re trying something which I really don’t like. It’s a pretence.

You are trying to pretend the template code can be split into header file and implementation file. But because it can’t you have to cheat by including the implementation file in the header file. It’s less confusing if you don’t cheat or pretend and just have one file, the header file, with everything in it.

The precise reason that you get a redefinition is that you are compiling your cpp file, which includes your header file, which includes your cpp file again. So the content of the cpp file gets compiled twice.

In C and C++, #include behaves like a copy and paste. Everytime you see

it should be treated as if you literally retyped the whole file in that one spot. So if you compile MyQueue.cpp, the preprocessor will prepend the contents of MyQueue.h, which itself tacks on a duplicate of MyQueue.cpp evidenced by

and then follows the native content of MyQueue.cpp.

inside MyQueue.h, is the same as if you had written one big file with the contents of MyQueue.h, MyQueue.cpp and MyQueue.cpp again. (with the include of stack in there as well of course) That is why the compiler complained about functions getting redefined.

The Duplicate inserted from the

might also contain the line

but I think the include guards (ifndef,endif) protected against a recursive expansion since that did not seem to be an issue.

I would like to point out that putting all the implementation code and declaration code in the same file for templates is not the only solution, as others suggest.

You just have to remember that templates are generated at compile time and include them wherever they are needed. Like Aaron has pointed out, you can even force generate a template for a specific type or function so it’s accessible to all units.

In this way, the definition of a function can be embedded in an arbitrary module and the rest of the modules won’t complain that a function isn’t defined.

It is a suitable alternative to storing large implementations in header files that must be pasted around just to refer to the type (or function signature). And it works absolutely fine, for years now.

So for example, when I am ready to compile my big program, I might have a file called structures.cpp that I designate to implement lots of small structures I use, as well as instantiate all the templates for my project.

to generate all the other definitions the rest of the project’s modules would need.

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