foreword

I can abstract the whole world, but I cannot abstract you. Wants to make you a private constant so outside functions can't access you. I also want you to be a global constant so that I can call you throughout my lifetime. It's a pity that there is no such constant in the world, and I can't define you, because you are so specific in my heart.

Hello everyone, this column is the [Project Actual Combat] column, which is different from the [Underlying Library] column. We can find that the chapters "Problem Description" and "Project Display" have been added, which is very in line with the project development process and allows readers to understand the project more clearly. The problem to be solved, and the effect that the product can achieve. This column contains solutions to the project development process, which is the refinement of relatively mature and reliable methods for my project development. I will sort out the solutions to these problems and write this article to share with you. If you encounter similar problems, you can deal with them according to the solution in this article.

This column will continue to be updated and improved, and the column articles are weakly related (the dependencies between articles are weak, and there is no reading order). If you have any questions, you can private message me. If you are interested in this column, please pay attention. I will show you how to use the most concise code to realize complex functions.

·提示：本专栏为项目实战篇，未接触项目开发的同学可能理解困难，不推荐阅读。

1. Problem description

We have determined the general direction, communicated with the business department, and further determined that the label needs to support the following goals:
①The company has confidentiality requirements, and the label is inconvenient to display product information, but specific personnel can understand it.
②The serial number should be manually checked, with double guarantees to prevent manual intervention if it cannot be identified.