Ruby on Rails: Post.find(8) vs Post.where(:id => 8) statements, can't get comments for Post.where

Question

This brings the comments with post_id=8

@onepost = Post.find(8)
@allpostsWithAssoc = @onepost.comments

But this doesn't bring the comments with post_id=8, but why ?

@onepost = Post.where(:id => 8)
@allpostsWithAssoc = @onepost.comments

I get

undefined method `comments' for #<ActiveRecord::Relation:0x9ecfce4>

Answer 1

The result of @onepost = Post.where(:id => 8) is a collection (or Array) of all Post records which matched the condition, not the the record itself. try this:

@onepost = Post.where(:id => 8).first
@allpostsWithAssoc = @onepost.comments

Answer 2

.where returns a relation. Even if you know that only one object matches the criteria, it is still a collection.

From the docs

The where method allows you to specify conditions to limit the records returned, representing the WHERE-part of the SQL statement. Conditions can either be specified as a string, array, or hash.

Try

@onepost = Post.where(:id => 8).first
@allpostsWithAssoc = @onepost.comments

to pick the first of (potentially numerous) matched records.