Скачать или смотреть How to Correctly Use a Function from Another File in C+ + : The run1 Example

Learn how to declare and use functions from separate files in C+ + . This guide explains how to properly structure your code using headers so you can avoid errors and make your C+ + projects organized and functional.
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How to Correctly Use a Function from Another File in C+ + : The run1 Example

When coding in C+ + , you might find yourself needing to use a function defined in another file. This is a common scenario, especially as you start structuring larger projects with multiple files. However, trying to call a function from a different file can lead to confusion and errors if not handled correctly. In today’s post, we will explore how to properly utilize a function from another file, using the example of the run1 function found in run.cpp called from main.cpp.

The Problem

Let’s consider the code you have written in two separate files:

main.cpp

run.cpp

Here's the code in your main.cpp file:

[[See Video to Reveal this Text or Code Snippet]]

You’re trying to call the function run1() that is defined in run.cpp, which contains the following code:

[[See Video to Reveal this Text or Code Snippet]]

When you compile using the command g+ + main.cpp run.cpp, you receive an error message indicating that run1 was not declared in main.cpp. The error suggests that the compiler is not aware that run1 exists, leading us to the solution we need to explore.

The Solution: Using Function Declarations

To resolve the issue, we need to inform the compiler about the run1 function in main.cpp. This is typically done using a function declaration. Let’s walk through the steps.

Step 1: Create a Header File

Create a Header File: This file will contain your function declarations. For this example, let’s name it run1.hpp.

Add the Function Declaration: Inside run1.hpp, you should declare the function like this:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Include the Header File in Your Source Files

Now that you have a header file with the function declaration, you need to include this header in both main.cpp and run.cpp.

Include in main.cpp: Add the following line at the top of main.cpp:

[[See Video to Reveal this Text or Code Snippet]]

Include in run.cpp: Also include the header in run.cpp:

[[See Video to Reveal this Text or Code Snippet]]

Including the header informs the compiler about the existence of the run1 function before you call it in main.cpp.

Step 3: Review the Full Code Structure

After these changes, your files should be structured like this:

main.cpp:

[[See Video to Reveal this Text or Code Snippet]]

run.cpp:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Compile Your Code

Finally, compile your files together:

[[See Video to Reveal this Text or Code Snippet]]

If everything is set correctly, you should be able to run your program without any errors!

Conclusion

By using a header file to declare functions, you can easily work with multiple files in C+ + . This method not only helps you avoid compilation errors but also organizes your code for better readability and maintenance. If you ever change a function’s parameters or return type, using a header file will help keep your declarations consistent across all relevant files.

Now go ahead and try it for your own projects! Happy coding!