Associations Relationships in Console - ruby-on-rails

Question

Ok, trying to learn rails commands on associations relationships in console
So if I have User that has_many posts, and Posts that belongs_to user ...
That means all this should work, correct? And these are all the the methods added automagically for this particular relationship, correct?
1. user.posts
2. user.posts=(posts)
3. user.posts << post
4. user.posts.delete(post)
5. user.posts.empty?
6. user.posts.size
7. user.post_ids
8. user.posts.clear
9. user.posts.find
10. user.posts.build(attributes={})
11. user.posts.create(attributes={})
user is: user = User.create(:name => "Michael")
result is: #<User id: 3, name: "Michael", created_at: "2016-06-21 16:52:22", updated_at: "2016-06-21 16:52:22">
&
post is: post = Post.create(:body => "body of txt")
result is: #<Post id: 3, user_id: 3, body: "body of txt", created_at: "2016-06-21 16:53:51", updated_at: "2016-06-21 16:58:38">
1. For user.posts, I get this:
#<ActiveRecord::Associations::CollectionProxy [#<Post id: 3, user_id: 3, body: "body of txt", created_at: "2016-06-21 16:53:51", updated_at: "2016-06-21 16:58:38">, #<Post id: nil, user_id: 3, body: "txt of body2", created_at: nil, updated_at: nil>]>
2. For user.posts=(posts), I get this:
NameError: undefined local variable or method posts' for main:Object and a whole bunch more of rbenv stuff
3. For user.posts << post, I get this:
#<ActiveRecord::Associations::CollectionProxy [#<Post id: 3, user_id: 3, body: "body of txt", created_at: "2016-06-21 16:53:51", updated_at: "2016-06-21 16:58:38">, #<Post id: nil, user_id: 3, body: "txt of body2", created_at: nil, updated_at: nil>, #<Post id: 3, user_id: 3, body: "body of txt", created_at: "2016-06-21 16:53:51", updated_at: "2016-06-21 16:58:38">]>
5. For user.posts.empty?, I get this:
false
6. For user.posts.size, I get this:
3
7. For user.post_ids, I get this:
[3, nil, 3]
9. For user.posts.find, I get this:
ActiveRecord::RecordNotFound: Couldn't find Post without an ID
10. For user.posts.build(attributes={:body => "random body of txt"}), I get this:
#<Post id: nil, user_id: 3, body: "random body of txt", created_at: nil, updated_at: nil>
Interesting thing about the one above is that when I do Post.all, that doesn't show up! But if I do user.posts, it does show up in that ...
11. For user.posts.create(attributes={}), I get this:
=> #<Post id: 4, user_id: 3, body: "body of text via create method", created_at: "2016-06-21 17:49:50", updated_at: "2016-06-21 17:49:50">
4. For user.posts.delete(post), I get this:
(0.3ms) begin transaction
SQL (0.6ms) DELETE FROM "posts" WHERE "posts"."id" = ? [["id", 3]]
(1.8ms) commit transaction
=> [#<Post id: 3, user_id: 3, body: "body of txt", created_at: "2016-06-21 16:53:51", updated_at: "2016-06-21 16:58:38">]
8. For user.posts.clear, I get this:
DELETE FROM "posts" WHERE "posts"."user_id" = ? [["user_id", 3]]
Which means now, when I run this: user.posts, I get this:
#<ActiveRecord::Associations::CollectionProxy []>
So, as you can see from above #2 doesn't work ... as well #9. Why not?
Thanks in advance for your help!
EDIT in response to answer (easier for clarification)
ok, I did posts = user.posts which resulted:
#<ActiveRecord::Associations::CollectionProxy [#<Post id: 5, user_id: 3, body: "body of txt", created_at: "2016-06-21 18:00:57", updated_at: "2016-06-21 18:01:11">, #<Post id: 6, user_id: 3, body: "body of txt2", created_at: "2016-06-21 18:22:02", updated_at: "2016-06-21 18:22:36">]>
then I did user.posts=(posts) which resulted the same answer as above.
But when I ran posts = Post.where(user: user), I got this:
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: posts.user: SELECT "posts".* FROM "posts" WHERE "posts"."user" = 3
Also, when I ran user.posts = posts, I got this:
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: posts.user: SELECT "posts".* FROM "posts" WHERE "posts"."user" = 3
In regards to user.posts.find(Post.last.id), it worked if I did this:
user.posts.find(Post.last) but if I did something like this:
user.posts.find(Post.last.6), I got this:
SyntaxError: (irb):121: no .<digit> floating literal anymore; put 0 before dotuser.posts.find(Post.last.6)

Answer 1

For #2
You need to define what "posts" is.
If you are trying to "set" posts
posts = user.posts
If you want to do a comparison on the two you would do:
posts = Post.where(user: user)
user.posts == posts #should be true
For #9
You need to pass something into your find method:
user.posts.find(Post.last) #this returns an object if "user" created Post.last
Hope this helps!
Edit:
You can't do user.posts=(posts) because you set data with an array, hash, string, integer, etc.
An equals comparison operator should have 2 ='s. That was my mistake and I have corrected the post.