発生した問題 Rails5.1を使ってみようと思い、いつものようにコードを書いていると、大量のwarningが出てることに気づいた。 DEPRECATION WARNING: The behavior of `attribute_changed?` inside of after callbacks will be changing in the next version of Rails. The new return value will reflect the behavior of calling the method after `save` returned (e.g. the opposite of what it returns now). To maintain the current behavior, use `saved_change_to_attribute?`
![ActiveRecordのchanged?が非推奨になっている - Qiita](https://cdn-ak-scissors.b.st-hatena.com/image/square/41a4451f3ef97991a0add603076d0b300df4ee62/height=288;version=1;width=512/https%3A%2F%2Fqiita-user-contents.imgix.net%2Fhttps%253A%252F%252Fcdn.qiita.com%252Fassets%252Fpublic%252Farticle-ogp-background-412672c5f0600ab9a64263b751f1bc81.png%3Fixlib%3Drb-4.0.0%26w%3D1200%26mark64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTk3MiZoPTM3OCZ0eHQ9QWN0aXZlUmVjb3JkJUUzJTgxJUFFY2hhbmdlZCUzRiVFMyU4MSU4QyVFOSU5RCU5RSVFNiU4RSVBOCVFNSVBNSVBOCVFMyU4MSVBQiVFMyU4MSVBQSVFMyU4MSVBMyVFMyU4MSVBNiVFMyU4MSU4NCVFMyU4MiU4QiZ0eHQtYWxpZ249bGVmdCUyQ3RvcCZ0eHQtY29sb3I9JTIzMjEyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTU2JnM9NzliMjdiZjQwZTlkOWRkMjU1Nzk5NDRhN2I3MzA5YjY%26mark-x%3D142%26mark-y%3D57%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZoPTc2Jnc9NzcwJnR4dD0lNDBrYXRvMjIyMiZ0eHQtY29sb3I9JTIzMjEyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTM2JnR4dC1hbGlnbj1sZWZ0JTJDdG9wJnM9YmYyNDI4OGI2ZmI0YmVkY2FmMGU4MWZhZTJiMjRmZTc%26blend-x%3D142%26blend-y%3D486%26blend-mode%3Dnormal%26s%3Db90d69e469399493bae2e26ac64f59dc)