The lecture content was a bit disappointing. I thought it would be a practical code that could be used right away in practice, but it was a bit disappointing. Also, while the beginning was written step by step, from the middle to the latter part, it was a bit disappointing that it just pasted the source code and gave a rough explanation. It would have been better to understand if it had been written step by step, but since it was too fast to paste the code and explain it, I missed a lot of parts and had to go back and look at them. However, for those who lack the basics or do not have a basic understanding of design patterns, I think they will get the feeling that this pattern is implemented this way. Anyway, it is an overall disappointing lecture with poor quality.