Скачать или смотреть Resolving the Common Can't locate object method "new" Error in Perl OOP

A guide to troubleshoot and resolve the "Can't locate object method 'new'" error in Perl object-oriented programming. Learn how to correctly load your packages to avoid common pitfalls.
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This video is based on the question https://stackoverflow.com/q/69467983/ asked by the user 'valentine' ( https://stackoverflow.com/u/15604525/ ) and on the answer https://stackoverflow.com/a/69468447/ provided by the user 'ikegami' ( https://stackoverflow.com/u/589924/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the Common Can't locate object method "new" Error in Perl OOP

Learning Perl, especially object-oriented programming (OOP), can sometimes throw unexpected challenges your way. One common error that beginners encounter is the message: Can't locate object method "new" via package "Stack01Lib". If you’ve found yourself scratching your head over this issue, you're in the right place! In this post, we’ll dive into what causes this error and offer you clear, step-by-step instructions on how to resolve it.

Understanding the Problem

When you attempt to create an object from a class in Perl, you typically call a "new" method. In your case, you successfully defined a new method inside your Stack01Lib package. However, when trying to use this method in your main program (Main.pl), you receive an error indicating that Perl cannot find the new method. The good news? This error usually stems from an oversight in loading the package correctly.

Analyzing the Code

Here’s a look at the pertinent parts of your code:

Main.pl

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

Stack01Lib.pm

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

Despite your logical implementations, the error indicates a deeper issue relating to file loading and paths.

The Cause of the Error

Incorrect Loading of Packages

The crucial part that is likely causing the error lies in how you're altering the -INC array, which tells Perl where to look for modules. By adding . (current directory) at the beginning of -INC, you may not be referencing the correct directory needed to locate Stack01Lib.pm.

Solution: Correctly Loading the Package

To ensure that Perl knows exactly where to find your Stack01Lib package, modify the code in your Main.pl. Follow these steps to resolve the error:

Use FindBin: This module will help you load the correct file path. Replace your BEGIN block with the following line:

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

This code snippet ensures that the script's directory is included in your module search path.

Alternative, Simplified Approach: You can simplify the code even further with:

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

Updated Example

Once you make this modification, your Main.pl should correctly load the Stack01Lib package without the Can't locate object method "new" error.

Final Thoughts

By correctly referencing the location of your package, you eliminate the risk of encountering the common error of not being able to locate the new method. This is a crucial step for anyone diving into Perl's OOP, allowing you to focus on learning how to create and manage your objects effectively. Remember, troubleshooting this type of error is a natural part of the coding journey, and each challenge helps you grow more proficient in your programming skills.

Now that you’ve resolved this issue, you’re one step closer to mastering Perl OOP. Happy coding!