So, one of the most frustrating things for me is trying to get the dynamically named migration file after it is created in order to manipulate it in a Ruby on Rails application template.
The problem arises when I run something like run "rails g migration CreateSettings" and then want to replace the created migration file with a pre-made migration file that has default values and null: false etc spelled out. It is quite difficult to know exactly what the file name is as the dynamic timestamp is down to the second.
I did a lot of research through StackOverflow and online and many people kept pointing to doing a Dir.glob to find the file, but the problem with that is that the name is dynamically created and if I have multiple migration files in there, I need to make sure that it is grabbing the correct file to replace.
QUESTION:
What is the best way with Ruby syntax to get the full file name of a dynamically created migration file following a rails g migration call? Say that the file was created after calling run "rails g migration CreateSettings", thus the dynamic name will follow the naming syntax: YYYYMMDDHHmmss_create_settings.rb
VERSIONS
Using Rails -v 6.1.3
Using Ruby -v 2.7.1p83
After a lot of research and trial and error, this is the solution that I came up with.
After running run "rails g migration CreateSettings" I then run this Ruby Code:
1. Dir.chdir('db/migrate/') {
2. Dir.glob('*.rb').each {|filename|
3. if filename.include? "create_settings"
4. file_location = 'db/migrate/' + filename
5. end
6. }
7. }
What this code does is:
(line 1) Changes the directory to look in to the migration folder.
(line 2) Within that directory it finds all files with an rb extension and starts to go through them one at a time (the each statement) with every iteration giving the new filename to the variable filename
(line 3) Checks to see if the filename string includes the string "create_settings"
(line 4) If it does include that string, it saves a new variable for the file path (location)
(lines 5-7) closes the circuits ;-)
Since there should only be one migration file for creating settings, this works. For anyone else using this in the future, make good use of naming conventions. For instance, if you add a new field for the Rails app name to the settings table, you should run the migration "AddAppNameToSettings" NOT "AddFieldToSettings". Because if you do this again and have once again have the second migration name of "AddFieldToSettings", you will have two migration files with different timestamps but with "add_field_to_settings" in the title and the above code will find both files.
I hope that my research and time can be of help to others in the future saving you the time it took me to research this.
Happy coding!
What is the best possible way to change name of table using migration and change name of all the files like controller, model and associations?
Will there be any issue when someone will try to run rails:db:migrate after cloning my repo?
What is the best possible way to change name of table using migration
To change the name of a table, you can run:
$ rails g migration change_[old_table_name]_to_[new_table_name]
Within the change method in the migration file generated, add this:
def change
rename_table :[old_table_name], :[new_table_name]
end
Change [old_table_name] and [new_table_name] in both cases.
(This part of the question has been answered here.)
will there be any issue when someone will try to run rails db:migrate after cloning my repo?
Nope. Keep the old migration files in place and generate a new one. That's the benefit of database migrations.
What is the best possible way to change name of all the files like controller, model and associations?
It's generally not too big of a deal to change a model name. Many text editors have the ability to search and replace within a directory.
And I would manually rename the filenames.
Here's a set of more detailed steps to make sure you've hit everything that needs to be changed.
I have created a class using scaffold in rubymine and did db migrate. Now I need to add one more instance variable (one more column to table in db) to the same class. How do I do this using rubymine (not from command-line) without destroying the class?
I don't think I understand the real issue here.
Would you not just rollback the current migration modify the migration in db/migrate (N) and add the column you want, then update the views for the model (since you've used a scaffold)? Once you do that, you would migrate again. Either that, or you'd create a new migration that adds the column you want– however, given that you've obviously just started this app, I see no reason to add an additional migration simply for this.
Update: The Question is Still Open, any reviews, comments are always welcome
I am having an existing rails project in which some important files and directories has been missed.
project rails version (2.3.8) i found it in environment.rb
currently what i am having is
app
controllers (already fully coded)
helpers (already fully coded)
models (already fully coded)
reports (already fully coded)
views (already fully coded)
config ---> default configurations (already fully coded)
lib ---> contains nothing
public --> contains images and scripts (already fully coded)
script ---> contains server,runner,plugin,dbconsole....
app directory fully contains working state of codes, app/model contains more than 100 .rb files , so i assume it will be more than 100 tables
the mainly missing things are db directory, .gem file, rake file, doc, test, vendor, database,schema.rb and migrations
Note:
i don't have the table schema and database for that project
i am in Need to generate tables or complete database from models and views and
i am looking for reverse engineering kind of stuff for generating db schema from models or views
I am newbie to rails and i am from java background , in java by using hibernate there is an pojo(model in rails) to database option available, i am looking for similar kind of stuffs for rails , and my main aim to run that project , so guys please help me.
To recreate the database schema, it will take quite a bit of time.
You can get a lot of information about the database in the app/models, app/controllers app/views directory.
You should know that ActiveRecord does not require you to explicitly list all the attributes of a model. This has important implications - you can only infer what attributes you still have to add to the database, based on whether an attribute is referred to! This means doing this will be a bit of an ART. And there are no CLEAR steps to complete this work. But below are some rules which you can use to HELP you.
This is a BIG project, below are guidelines, rules and tips to help you. But be aware that this could take a long time, and be frustrating at times to get this done.
What Tables you need:
Each table will normally have a matching ActiveRecord::Base model. So in the app/models directory, check each file, and if the class inherits from ActiveRecord::Base, it is an extra table.
The table name is by default a pluralized snake case version of the name of the class.
class UserGroup < ActiveRecord::Base # for this class
the name of the table is user_groups. Notice it is plural, and instead of camel case, it is lowercase, with underscores to separate the words.
All these tables will have an "id" integer column. By default, the tables also have a "created_at", and "updated_at" column of type datetime.
Associations and foreign keys:
You can infer what foreign keys exist by the associations in the Models. All associations are explicitly listed, so this is not too hard.
For example:
class UserGroup < ActiveRecord::Base # for this class
belongs_to :category
This means that the user_groups table has a column named "category_id", which is a foreign key for the categories table.
This means that the Category model likely has an inverse relationship (but no extra column):
class Category < ActiveRecord::Base
has_many :user_groups
The main other association is the has_many_and_belongs_to association. Eg.
class A < ActiveRecord::Base
has_and_belongs_to_many :bs
end
class B < ActiveRecord::Base
has_and_belongs_to_many :as
end
This means that there is a join table to add called "as_bs" (as and bs are sorted alphabetically), with the foreign keys "a_id" and "b_id".
All foreign keys are integers.
Attributes
Ok, so that's the table associations. Now for the normal attributes...
You should check the app/views/user_groups/ or other similar app/views directories.
Inside you will find the view templates. You should look at the _form.html.erb templates (assuming it is .erb templates, otherwise it could be .haml etc templates).
The _form.html.erb template, if it exists, will normally have many of the attributes listed as form fields.
In the form_for block, check if it says something like f.text_field :name, it means there is an attribute/(column in the table) called "name". You can infer what type the column should be by what type of field it is. Eg. in this case, it is a string, so maybe a VARCHAR(255) is appropriate (referred to as string in Rails).
You might also need to infer what type is appropriate based on the name of the attribute (eg. if it mentions something like :time, then it is probably either of type Time or DateTime).
This may give you all the other attributes in the table. But in some cases, you might miss the attributes. If you find a reference to other attributes in the controller, eg. app/controllers/user_groups_controller.rb, then you should add that as a column in your table. You can leave this until the end when you test it though, because when you test it, if an attribute is missing, then it will throw a NoMethodError for the object of the relevant model. Eg. if it says that #user_group variable, of class UserGroup, is missing a method named title, then it probably is missing a column named "title" of type string.
Recreate your migration/database
Ok, so now you know what the database tables and column names and types should be.
You should generate/recreate a migration for your database.
To do this, just use the command rails generate migration RecreateTables.
Then you should find a file in db/migrate/???_recreate_tables.rb.
Inside, start writing ruby code to create your tables. Reference for this can be found at http://guides.rubyonrails.org/migrations.html.
But essentially, you will have something like:
class RecreateTables < ActiveRecord::Migration
def up
create_table :user_groups do |t|
t.string :name # adds a string (VARCHAR) column called "name"
t.text :description # adds a textarea type column called "description
t.timestamps # adds both "created_at" and "updated_at" columns for you
end
end
def down
drop_table :products # this is the reverse commands to undo stuff in "up"
end
end
To recreate your Gemfile:
Start by adding a default Gemfile. This can be done by using rails new testapplication somewhere to create an empty rails application. Then copy the Gemfile to your actual application. It will get you started by including rails and other common gems.
It is VERY hard to work out exactly what gems are needed. The best you can do is try adding them one by one as you look through the code.
Again, here, MethodNotFound errors are your FRIEND. When you test the application, based on the gems you have added, it might detect some missing methods which might be supplied by gems. Some missing methods on models might indicate missing gems (or they might indicate missing fields/columns in the database). However, missing methods on Controller or ActiveRelation classes are VERY likely because of missing gems.
You will have to look through the code and try to infer what gems to add.
If it uses methods like can, can?, and has a file app/models/ability.rb, then you need gem 'cancan'. If it calls devise in a model, it needs gem 'devise'. Many common gems can be seen at http://ruby-toolbox.com.
After adding gems to your Gemfile, you should run bundle on your command line to install the new gems before testing again. When you test it again, you should restart your test server. Rerun bundle exec rails server to start a local test server on localhost:3000 or something like that.
You can simply copy the Rakefile from rails new testapp, and it will probably include everything you need.
Missing Tests
The missing test/ directory is not relevant to your actual application. It is not required to run the application. However, it does hold automatic scripts to test your application. You will have to re-write new tests if you want to automatically test your application. However for the purpose of getting your application back up, you can ignore it for now.
Missing vendor directory
Some extra code is not installed as a gem, but as a plugin. Anything installed as a plugin is lost if you don't have the vendor directory. As with gems, the best you can do is try to infer what might be missing, and re-download the missing plugin, either re-installing the plugin, or using a gem replacement.
Additional tips:
Try reading some of the comments which might name some of the gems used.
If a method or set of methods are missing, that you think are not database fields/columns, it might be due to a missing gem. The best thing to do is to search google for those method names. Eg. if it is missing "paginate", you can search "rails paginate gem", and see what likely gems you might need. This example will probably come up with "will_paginate", and "kaminari". Then you have to try and infer which of the gems are required. Maybe do a grep will_paginate app -r on the command line to see if it is using will paginate. The grep command searches for the string "will_paginate", in the directory called "app", -r makes it do this recursively for all files
Even though rails is a full stack web framework it would work with out some parts as well, if you wish to,
Ex: in your case
db - directory is there for keep the migrations to create you DB/tables, but if you are using a legacy DB or the database stuff is handled by DB administrators, you might not want it. (you can simply connect to the DB via database.yml file)
Gem file is helping you to keep all the gems (libraries) in one place as you do with Maven (in java)
test, again if you done write test cases (which is absolutely a bad idea), you done need this
vendor, is for 3rd party plugins and doc is for documentation, so same rule applies, if you done need them you can skip them
Hibernate in rails called "Activerecord", same concept, a model is bind with a database table (technically model represents a raw in the table)
So if you really want them add them but if not just leave them
BUT, I think having a proper Gem file and test cases is a must
welcome come to Rails
HTH
In the following, I assume you already know how to:
dump your database schema into an SQL file
start a Rails console (rails c)
generate a Rails migration
Here's what I think you should do.
Identify which of your classes correspond to physical tables (you mention some views in your question, which leads me to believe a subset of your models are bound to database views instead of actual tables). To do this you need to match the definitions of your models (classes which extend ActiveRecord::Base) to CREATE TABLE statements in your schema dump. For instance, class Person in your Ruby code matches to CREATE TABLE people in your DB schema dump.
Once you identified those models (class names), you start up a Rails console and you type those model names, one at a time, and press Enter. The console output for a model called Person would presumably look like this:
>> Person
=> Person(id: integer, first_name: string, last_name: string)
You then take what's inside the parentheses, strip the leading id: integer,, get rid of commas, get rid of those blanks after the colons, thus obtaining something like this:
first_name:string last_name:string
Having done this, the command to generate the migration would look like this:
rails g migration Person first_name:string last_name:string
You then start a new Rails project somewhere else, perform all of these migrations and inspect the contents of db/migrate. Your migrations are most likely 90% done, what you still need to do is replace some instances of t.integer with t.references, and other minor stuff that's completely domain-specific and impossible to capture in a generic answer.
HTH.
I have a rails project that uses an old versions of the FlexImage plug-in to handle images.
In the old version that image data was stored in a column called "data", in the new version that column must be named "image_file_data".
I wrote a migration to rename the column, but when I try to run the migration, my guess is that rails tries to load the models, which then automatically check to see if the valid column is there (which it isn't) and that throws an error which halts the migration.
I would guess that my problems would be solved if I never loaded the model classes in question and just wrote some sql to rename the columns. But the following line doesn't work, since rails still tries to load the model.
Apartment.connection.execute "ALTER TABLE logos CHANGE DATA image_file_data MEDIUMBLOB;"
Oops, I figured it out. I was calling
model = (table_name.to_s).classify.constantize
Earlier, and this was causing the model to load