Скачать или смотреть Resolving C++ Error: No Match for 'operator[]' — Understanding and Fixing Subscript Operator Issues

Learn how to fix the `C++ error: no match for 'operator[]'` by understanding operator overloading and the proper usage of class methods for indexing.
---
This video is based on the question https://stackoverflow.com/q/70473909/ asked by the user 'harumichi113' ( https://stackoverflow.com/u/7690586/ ) and on the answer https://stackoverflow.com/a/70473986/ provided by the user 'Vlad from Moscow' ( https://stackoverflow.com/u/2877241/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: C++ error: no match for 'operator[]' (operand types are 'const my_array_over' and 'size_t' {aka 'long unsigned int'})

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding the C++ Error: No Match for 'operator[]'

If you've encountered the error no match for 'operator[]' (operand types are 'const my_array_over' and 'size_t') while working with a custom class in C++, you're not alone. This error indicates that the compiler cannot find an appropriate subscript operator for your class. This guide aims to dissect this issue and provide you with clear solutions to ensure your code runs smoothly.

The Problem

The error arises when you attempt to access elements of an instance of your class using the subscript operator ([]). In the provided code, the following line is causing the problem:

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

Why the Error Occurs

In your class my_array_over, the subscript operator is not defined, which means the compiler does not know how to handle expressions like a2[i]. The correct way to retrieve an element from your custom class is by using a method specifically designed for this purpose, such as get(), since you have not overloaded the subscript operator.

Solution: Define the Subscript Operator

To resolve this issue, you have two options:

1. Use Existing Methods

You can simply replace the problematic line with a call to your get() method, which is already defined in your class:

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

This change will eliminate the error since you're now correctly using the method to access elements.

2. Add Operator Overloading

Alternatively, if you want to keep the syntax a2[i], you need to overload the subscript operator in your class. Here’s how you can do that:

Implementing the Overload

Add the following methods to your my_array_over class:

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

Explanation of the Overloads

Const Overload: This version allows you to access elements in a read-only manner when the object is constant. This is helpful when you want to prevent modification of the data.

Non-const Overload: This version allows modification of the elements. This is useful when you have mutable instances of your class.

Final Code Implementation

With either of the above solutions applied, your foo function can now correctly access the elements of my_array_over without errors.

Here’s how your updated relevant code should look:

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

Or, using the operator overloading:

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

Conclusion

By understanding the cause of the no match for 'operator[]' error and implementing one of the proposed fixes, you can enhance your class's usability and avoid compilation issues. Both solutions yield the same outcome—allowing you to utilize the syntax you prefer while maintaining proper functionality.

With these insights, you should now be equipped to handle similar operator overloading issues in the future!