Why does the Rails increment method doesn't save the changes?

Question

I have this code to implement a thumbs up/down functionality in my rails app

if params[:vote][:type] == "up"
    answer = Answer.find_by_id(params[:vote][:id])
    answer.increment(:ups)
    render text: answer.ups
end
if params[:vote][:type] == "down"
    answer = Answer.find_by_id(params[:vote][:id])
    answer.increment(:downs)
    render text: answer.downs
end

It doesn't give any error but the incremented value is not updated in the DB.

This code works properly in rails console.

Please help,

Thanks in advance

score 3 · Answer 1 · answered Jun 05 '13 at 10:35

3

this is by design. The method increments the attribute but does not save. Use increment! (bang version) if you want to save as well.

answered Jun 05 '13 at 10:35

m_x

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the increment! method returns true still the DB doesn't reflect the changes – Akshay Takkar Jun 05 '13 at 10:42
if it does not act as documented, i guess your problem lies somewhere else. Try to increment the thing manually and save. If it does not work, maybe there's a problem with your column definition. – m_x Jun 05 '13 at 10:58

score 1 · Answer 2 · answered Jun 05 '13 at 10:31

1

Check it once

if params[:vote][:type] == "up"
    answer = Answer.find_by_id(params[:vote][:id])
    answer.to_i.increment(:ups)
    render text: answer.ups
elsif params[:vote][:type] == "down"
    answer = Answer.find_by_id(params[:vote][:id])
    answer.to_i.increment(:downs)
    render text: answer.downs
end

answered Jun 05 '13 at 10:31

Ganesh Kunwar

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Answer is a model with attributes like answer_data, ups, downs etc..so i can't convert it to integer..i even tried calling answer.save after answer.increment but it still doesn't work – Akshay Takkar Jun 05 '13 at 10:36

Muntasim · Accepted Answer · 2013-06-05T11:16:21.117

1

could you please write the schema of your model, I mean fields with datatype

another migration with:

change_column :answers, :ups, :integer, :default: 0
change_column :answers, :downs, :integer, :default: 0

might help you

edited Jun 05 '13 at 11:16

answered Jun 05 '13 at 11:10

Muntasim

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create_table "answers", :force => true do |t| t.text "answer_data" t.integer "ups" t.integer "downs" t.integer "question_id" t.integer "user_id" t.datetime "created_at", :null => false t.datetime "updated_at", :null => false end – Akshay Takkar Jun 05 '13 at 11:11
increment/decrement fields should have default value 0 otherwise it wont work – Muntasim Jun 05 '13 at 11:13
i've used a method that keeps 0 as the value of up / down. the method is called before saving the model – Akshay Takkar Jun 05 '13 at 11:15
Oh yea there's the problem..before saving a method runs that resets the values to 0..sorry..was a silly mistake – Akshay Takkar Jun 05 '13 at 11:17
I have tested keeping null as default value. increment! method is working please make sure answer.increment!(:ups) is executed, I mean if params[:vote][:type] == "up" returns true – Muntasim Jun 05 '13 at 11:26
yea..ran the migration..everything is working fine..thanks again – Akshay Takkar Jun 05 '13 at 11:35

Why does the Rails increment method doesn't save the changes?

3 Answers3