Updating associated record attribute doesn't work

Question

A post has many comments. In my code I am trying to change an attribute of the first comment like so:

post = Post.find(id)
post.comments.first.title # "initial title"
post.comments.first.title = "foobar"

post.comments.first.title_changed? # false
post.comments.first.title # "initial title"

Is this an expected AR behavior? If yes, how can I change attributes of associated records?

Answer 1

First, assign the comment object to a variable, then make the change to that variable and save

post = Post.find(id)
comment = post.comments.first
comment.title = "foobar"
comment.title_changed? # true
comment.save

Answer 2

Yes, it is expected. post.comments.first.title = "foobar" just assigns the title but not saves it.

Right way to update is post.comments.first.update(title: "foobar").

Or you need to post.comments.first.save after assigning a new title