Question

It worked before but why it isn’t now? I was trying to to create a post by only the signIn user.Or is it my routing problems?
My routing is
resources :users do
resources :microposts
end

microposts controller

def create
    @micropost = current_user.microposts.build(params[:micropost])
    if @micropost.save 
        flash[:success] = "Post created!"
        redirect_to @micropost
    else
        render 'new'
    end
end

new.html.erb

 <%= form_for @micropost do |f| %>
<%= render 'shared/error_messages', :object => f.object %>
<%= f.hidden_field :user_id, :value => current_user.id %>

<%= f.label :title %><br />
<%=h f.text_field :title %><br />

<%= f.label :content %><br />
<%=h f.text_area :content, :row => 30, :cols=> 30 %><br />

<%= f.label :category %><br />
<%=h f.text_field :category %><br />

<%= f.submit "Post" %>

microposts model

class Micropost < ActiveRecord::Base
belongs_to :users
default_scope :order => 'microposts.created_at DESC'

attr_accessible :title,:content,:category

validates :user_id, :presence => true
validates :title,    :presence => true,
                     :length => {:maximum =>500}                            
validates :content,  :presence => true,
                     :length => {:maximum =>3000}                           
validates :category, :presence => true

end

migration microposts

class CreateMicroposts < ActiveRecord::Migration
  def self.up
create_table :microposts do |t|
  t.string :title
  t.string :content
  t.string :user_id
  t.string :category

  t.timestamps
end
    add_index :microposts, [:title, :created_at, :category]
  end

  def self.down
    drop_table :microposts
 end
end

Answer 1

Your user model needs:

has_many :microposts