Dirty checking is broken for string join

Don't see an easy fix, but a workaround is s/<</+=/

This is the same problem as http://rails.lighthouseapp.com/p...

This ticket is invalid. Dirty checking will only currently work if you replace an attribute with a new value, not edit it in place.

Instead you should do:

t = Topic.find(1)
t.title_will_change!
t.title = t.title << "new"
t.changed?
# => true

I know will_change can resolve this issue as a temp solution, however, how to explain the inconsistent of string / numeric field?

create_table :topics do |t|

t.string :title

t.integer :score

end

t = Topic.find(1)

t.title = t.title.contact(33)

t.changed?

1. => false

t.score = t.score.*(33)

t.changed?

1. => true

What does t.title.contact(33) do?

If you set the title to the same value it was before, changed? will return false.

If you set it to a new value, it should return true.

I've tested this and I can confirm it.

A little something to think about before someone actually spends time on creating a patch that isn't really necessary:

With t.title << "new", I would actually think that the title changes. t.title = t.title << "new" looks intriguing to me because it looks like it does the actual assignment twice. IMO you shouldn't "reassign" the variable when using the << operator.

What would make sense, though, is having something like t.title = t.title + "new" or its short form, t.title += "new". Both of them actually work perfectly fine and t.title_changed? returns true.

The important question to ask is whether one should use something misleading like t.title = t.title << "new" when there's two valid ways around that even look more logical. One is, as I said, t.title += "new" and the other would be to use t.title_will_change! t.title << "new".

I can confirm this as well.

There's some discussion on whether something is "changed" if the contents are changed. To me that seems like a valid case. I was working on a serialized array to a model, and if I do something like:

@

my_model.serialized_array << 'new pushed element'

my_model.changed # intuitively this should return ["serialized_array"]

@

I feel that this is a common scenario where a serialized array needs modification, and the very idea of something being modified is, well, a change.