[Rails] I don't know how to use the model ...

Background

Currently, I am attending a certain programming school, but when implementing the search function (search window), I was told to use a model and a controller for processing properly. Eh ... It's okay to use all the controllers ... (Of course, I'm actively using them separately now!)

** ・ Controller… Data is acquired from DB, saved, and only simple processing is described ** ** ・ Model: Describes the value obtained from the DB that performs complicated processing ** I use it properly with the image.

However, I didn't want to use it because I couldn't understand why the ** "processing catalog" ** set in the model could be used with the controller, no, I couldn't. (This article is not an article to explain the search function. It is just a summary of my mind about how to use the model.)

Implementation of search function

models/tweet.rb (model)

class Tweet < ApplicationRecord
  validates :text, presence: true
  belongs_to :user
  has_many :comments

  def self.search(search)
    return Tweet.all unless search
    Tweet.where('text LIKE(?)', "%#{search}%")
  end

end

• The 2nd and 4th lines are not necessary, but I intentionally leave them so that you can understand "I'm writing on the model". Also, please forgive me for the mysterious line breaks that are included for easy viewing.

controllers/tweets_controller.rb (controller)

class TweetsController < ApplicationController

  def search
    @tweets = Tweet.search(params[:keyword])
  end

end

Understanding point

① What is the "search" method of the controller?
(Not listed in the reference ??)

It's not listed in the reference. Because ** "method made by model" **! !!

② What is the model "self"?
(When you google, it's commonly called a "class method" ...)

――I won't explain in detail here, but ** class name is assigned ** to this one. (The expression assignment is used for clarity) --Look at the first line of tweet.rb (tweet model). Did you understand the class name? ――In other words, "self.search (search)" is ** "" Tweet.search (search) "**. (Like I saw it somewhere)

③ Why can the controller use the "processing catalog" set in the model?
(Finally the main subject)

Did you understand somehow? ??

--The "Tweet.search (params [: keyword])" used in the controller is the same as the ** self.search (search) "** method you created in the model.

The identity of the method

In fact, various methods such as "find method" and "include method" that we often use Just like I made my own "search method" this time, ** Rails' ActiveRecord made it **! !!

** Each model inherits ActiveRecord **, so you can use methods in your controller! (Strictly speaking, class Tweet <ApplicationRecord <ActiveRecord :: Base) If you look at the first line of tweet.rb (tweet model), you can see it.

That guy

Well, it's getting longer, but there is one who hasn't solved it yet. Yes, what was "self = class method" after all?

Class methods are literally methods that can be used for "classes". Can you remember what a "class" was? ?? If you don't know, take a look at the first line of tweet.rb (tweet model).

** I still don't understand any more! !! Lol**

Acknowledgments

It may have been a bit confusing, but please forgive me because I have been programming for 2 months. (I was able to organize my head relatively.) I've written this for a long time, but thank you for reading to the end.

If the interpretation is wrong, I would be very grateful if you could let me know.

More and more.