Rails sort association proxy after new object is build - ruby-on-rails-4

Question

I have two models,
class User < ActiveRecord::Base
has_many :posts, -> { order('post.id') }
end
class Post < ActiveRecord::Base
belongs_to: user
end
For instance i'm having a #user and two posts associated. while doing #user.posts, the result be like.
[
[0] #<Post:0x0000000aa53a20> {
:id => 3,
:title => 'Hello World',
:comment => 'Long text comes here'
},
[1] #<Post:0x0000000aa53a41> {
:id => 5,
:title => 'Hello World 2',
:comment => 'Long text comes here too'
}
]
Now, I'm building one more extra object by doing #user.posts.build and
that the below result of doing #user.posts
[
[0] #<Post:0x0000000aa53a20> {
:id => 3,
:title => 'Hello World',
:comment => 'Long text comes here'
},
[1] #<Post:0x0000000aa53a41> {
:id => 5,
:title => 'Hello World 2',
:comment => 'Long text comes here too'
},
[2] #<Post:0x0000000aa53a50> {
:id => nil,
:title => nil,
:comment => nil
},
]
What i actually want is, to sort by object with nil first. The result should exactly look like,
[
[0] #<Post:0x0000000aa53a50> {
:id => nil,
:title => nil,
:comment => nil
},
[1] #<Post:0x0000000aa53a20> {
:id => 3,
:title => 'Hello World',
:comment => 'Long text comes here'
},
[2] #<Post:0x0000000aa53a41> {
:id => 5,
:title => 'Hello World 2',
:comment => 'Long text comes here too'
}
]
It can also be done by an custom method to sort by looping through each object. But don't want to write another method. The result should in Association Proxy and not an Array
Is it possible to achieve it in association proxy itself?

Answer 1

Suppose, you have the #posts variable where it contains the nil item.
#posts.sort{|i,j| i.id && j.id ? i <=> j : j.id ? -1 : 1 }
result => [nil, 3, 5]