Rails5 tips

README.md

@@ -7,6 +7,9 @@ Being impressed with the awesomeness of jstip repository, I came up with the ide
 Please feel free to send us a pull request with your Rails tip to be published here. Any improvements or suggestions are more than welcome!
 
 # Tips list
+- 31 - [Remove ambiguous column issue in rails 5](https://github.com/logeshmallow/rails_tips/blob/master/rails_tip/2016-11-31-Ambiguous_column_in_select_and_group_fix_in_rails5.md)
+- 30 - [Remove nil from hash in rails 5](https://github.com/logeshmallow/rails_tips/blob/master/rails_tip/2016-11-26-Remove_nil_from_hash.md)
+- 29 - [Retrieving the ids of the has_many or has_many_through relationships](https://github.com/logeshmallow/rails_tips/blob/master/rails_tip/2016-03-29-Retrieving_ids_from_relationship.md)
 - 28 - [Support for left outer join in rails 5](https://github.com/logeshmallow/rails_tips/blob/master/rails_tip/2016-03-10-left_outer_join_in_Rails_5.md)
 - 27 - [Render partial from cache faster](https://github.com/logeshmallow/rails_tips/blob/master/rails_tip/2016-03-09-rendering_partial_from_cache_faster.md)
 - 26 - [Increase productivity with console tricks](https://github.com/logeshmallow/rails_tips/blob/master/rails_tip/2016-03-08-Increase_productivity_with_few_tricks.md)

rails_tip/2016-11-26-Remove_nil_from_hash.md

@@ -0,0 +1,25 @@
+---
+title: Remove nil from hash using Hash#compact and Hash#compact!
+tip-number: 30
+tip-username: Logesh
+tip-username-profile: https://github.com/logeshmallow
+tip-description: We always had an issue when we send hash with nil value and now here is the option in ruby 2.4 to remove the nil using Hash#compact and Hash#compact!
+
+---
+
+
+
+
+We all would have faced removing nil value from array and hash and we had compact for removing nil from array and now in ruby 2.4, we also have option to remove it from hash
+
+```ruby
+
+    hash = { "username" => "logesh", "company" => nil}
+    hash.compact #=> { "username" => "logesh" }
+    hash #=> { "username" => "logesh", "company" => nil}
+
+    hash.compact! #=> { "username" => "logesh" }
+    hash #=> { "username" => "logesh" }
+```
+
+Since this comes with ruby itself, we even don't need rails to use this.

rails_tip/2016-11-31-Ambiguous_column_in_select_and_group_fix_in_rails5.md

@@ -0,0 +1,32 @@
+---
+title: Removing ambiguous column issue in rails 5
+tip-number: 31
+tip-username: Logesh
+tip-username-profile: https://github.com/logeshmallow
+tip-description: Whenever we have columns with same name in two table and query it, we face ambiguous column issue in select and group by and rails5 fixes it now
+
+---
+
+
+```ruby
+
+    users(:id, :name)
+    posts(:id, :title, :user_id)
+    comments(:id, :description, :user_id, :post_id)
+
+    >> Post.joins(:comments).group(:user_id).count
+    Mysql2::Error: Column 'user_id' in field list is ambiguous: SELECT COUNT(*) AS count_all, user_id AS user_id FROM `posts` INNER JOIN `comments` ON `comments`.`post_id` = `posts`.`id` GROUP BY user_id
+
+
+    users(:id, :name)
+    posts(:id, :title, :user_id)
+    comments(:id, :description, :user_id, :post_id)
+
+    >> Post.joins(:comments).group(:user_id).count
+    SELECT COUNT(*) AS count_all, "posts"."user_id" AS posts_user_id FROM "posts" INNER JOIN "comments" ON "comments"."post_id" = "posts"."id" GROUP BY "posts"."user_id"
+
+    => { 1 => 1 }
+
+```
+
+This shows that now both projection and Group By are prepended with the posts table name and hence fixing the conflict.