Is it possible to specify the column for an attribute? I have something like:
NAME, COUNTRY
The database is quite large and I have over a thousand columns which are capitalized like this. I want to refer to them as so:
attr_accessible :name, :country
Where :name = column NAME. I'd prefer Model.name rather than Model.NAME. It isn't possible to downcase every column name in the structure file.
Here is an idea to do the way you preferred.
Command to generate migration: (In my example, im applying this on Posts table. Change according to your table name)
rails g migrate RenameColumnsOfPosts
Below is the migration up method. Here taking all the column names and for each one I'm applying rename_column to make it downcase.
class RenameColumnsOfPosts < ActiveRecord::Migration
def up
Post.columns.map(&:name).each do |column_name|
rename_column(:posts, column_name, column_name.downcase)
end
end
def down
#You can do the opposite operation here. Leaving on you
end
end
As i didnt run it personally, it might need some changes. So start with it and let me know if facing any problem.
Please write code inside of model ,
it's just for demostration code,after you get it and update as per logic :
This Code inside of model :
...
attr_accessor :name,:country
before_save :fill_save
..
#assign variable like ...
def fill_save
self.NAME= self.name
self.COUNTRY= self.country
end
....
Related
Has anyone experienced this issue on mapping table in ActiveRecord when table name need a schema name as a prefix (oracle)?
Gemfile
gem 'activerecord', '4.2.4'
gem 'activerecord-oracle_enhanced-adapter', '1.6.7'
....
db_helper.rb
class Student < ActiveRecord::Base
self.abstract_class = true
self.table_name_prefix = 'OPT_ABC.'
self.table_name = 'STUDENT'
def self.list_student
puts Student.take(1) #testing
end
end
The actual table name looks like:
SELECT * FROM OPT_ABC.STUDENT;
I am able to connect to the database instance, but when the code gets line:
puts Student.take(1) # SELECT * FROM STUDENT LIMIT 1
I get the following error:
ActiveRecord::StatementInvalid:
table or view does not exist: SELECT "STUDENT".* FROM "STUDENT"
I am looking for solution on how to handle 'OPT_ABC." table prefix. Please share your solution.
It looks like the problem is that you're trying to use both self.table_name_prefix= and self.table_name= together when you should be using one OR the other.
First let's consider how both self.table_name_prefix= and self.table_name= work.
self.table_name_prefix=
According to the documentation, self.table_name_prefix= works by prepending the passed in value to the table name that ActiveRecord automatically generates based off of the name of the class.
So, if the class name is Student and you do self.table_name_prefix = 'OPT_ABC.', your table name will be OPT_ABC.STUDENTS. Note that the generated table name is plural (and ends in an s).
self.table_name=
According to the documentation, self.table_name= sets the table name explicitly. This means that it completely overrides the table name to the value that you pass in.
So, if you do self.table_name = 'OPT_ABC.STUDENT' your table name will be OPT_ABC.STUDENT.
So, given that, to set the table name to OPT_ABC.STUDENT, you should be able to simply pass the value into self.table_name like this:
class Student < ActiveRecord::Base
self.abstract_class = true
self.table_name = 'OPT_ABC.STUDENT'
def self.list_student
puts Student.take(1) #testing
end
end
In my rails model I have a JSON column which stores some meta information.
This is to be entered bu the user from a form.
Since the keys of the JSON column are not attributes of the model I cannot use them directly in form_for instead I need to define a virtual attribute.
Since this number of virtual attributes could grow to be arbitrarily lengthy I would like to use meta programming to define the attributes.
I did try the answer in this question however when I use the constant in my model I get an error saying that the constant is undefined. So I added the symbols for the keys in an array directly and iterate over them in the module. When I do this I get an error that says stack level too deep.
Please can someone help me out here?
If you are using PostgreSQL specific columns like hstore or json simply use store_accessor instead to generate the accessor methods. Be aware that these columns use a string keyed hash and do not allow access using a symbol.
class Model < ActiveRecord::Base
store_accessor :my_json_column, [ :key_1, :key_2, key_3 ]
end
What it doing under the hood? It has define write\read helper methods:
def store_accessor(store_attribute, *keys)
keys = keys.flatten
_store_accessors_module.module_eval do
keys.each do |key|
define_method("#{key}=") do |value|
write_store_attribute(store_attribute, key, value)
end
define_method(key) do
read_store_attribute(store_attribute, key)
end
end
end
# .....
store
I figured it out. I return the attribute as a key of the JSON column and it works fine now.
# lib/virtuals.rb
module Virtuals
%W(key_1 key_2 key_3).each do |attr|
define_method(attr) do
self.my_json_column[attr]
end
define_method("#{attr}=") do |val|
self.my_json_column[attr] = val
end
end
end
In my Model i just need to include that above module and it works fine in the form_for and updates correctly as well.
I had the following function. It worked, but I don't like the way it looked.
# in user.rb
def awarded_requests
Request.joins('JOIN application ON application.request_id = request.id').where('accepted = true AND application.user_id = ?', self.id)
end
Then I refactored it to something that's clearly an improvement, but probably not simplest possible form:
def awarded_requests
Request.find(self.applications.accepted.map(&:request_id))
end
Can this be simplified further?
If you set up has many relationship, you can filter out those requests by merging a scope.
class User
has_many :applications
def awarded_requests
Request.joins(:applications).merge(applications.accepted)
end
end
Note that applications.accepted is not an array of records but a scope. This is how Active Record represents a part of SQL query internally, therefore it can smartly combine a few of them.
I've been following this article to display ActiveRecord data in QtRuby. I've copied the BoatTableModel class from there(used my own code for the rest). In the article, BoatTableModel is defined to only support the Boat model, but except for the column definitions the code is quite generic. So, I've changed it so instead of having the columns defined there, I've made it take the columns from a column_names method, and define that methods in subclasses for each model.
Here is my code:
class QtArModel<Qt::AbstractTableModel
def initialize(items)
super()
#items=items
end
def rowCount(parent=nil)
#items.size
end
def columnCount(parent=nil)
column_names.length
end
def data(index,role=Qt::DisplayRole)
invalid=Qt::Variant.new
return invalid unless role==Qt::DisplayRole or role==Qt::EditRole
item=#items[index.row]
return invalid if item.nil?
v=item[column_names[index.column]]||""
return Qt::Variant.new(v)
end
def headerData(section,orientation,role=Qt::DisplayRole)
invalid=Qt::Variant.new
return invalid unless role==Qt::DisplayRole
v=case orientation
when Qt::Horizontal
column_names[section]
else
""
end
return Qt::Variant.new(v.to_s)
end
def flags(index)
return Qt::ItemIsEditable|super(index)
end
def setData(index,variant,role=Qt::EditRole)
if index.valid? and role==Qt::EditRole
s=variant.toString
item=#items[index.row]
if index.column.between?(0,column_names.length-1)
item[column_names[index.column]]=s
else
raise "invalid column #{index.column}"
end
item.save
emit dataChanged(index,index)
else
return false
end
end
end
class QtCoursesTableModel<QtArModel
def column_names
return [
:number,
:name,
:tutor_name,
:site,
:active,
]
end
end
class QtTasksTableModel<QtArModel
def column_names
return [
:course,
:ex_number,
:received,
:due,
:description,
:link,
:completed,
:file,
]
end
end
Now, when I display one model(doesn't matter which) - everything works just fine. However, when I display both models, each in it's own Qt::TableView - only the first one is displayed, and the other table view is blank.
I've tried different ordering, and the table that gets to display it's data is always the one which it's Qt::TableView is created first - the order of the creating the Qt models does not matter. Also, when I create the model object for the first table, but don't actually set it's model property to it, the second table displays it's data.
I've also tried to display the same model twice in two different table views - and it worked - for a split second, and then the second view's data disappeared.
I've also tried to copy-paste the QtArModel, change it's name, and make one of the models inherit from the copy. That did work - but it's obviously a huge code duplication, so I would really like to avoid that.
Now, my guess is that something in QtArModel is defined as a class member instead of instance member, making both model instances share something they shouldn't share. It has to be in QtArModel - because if it was higher in the inheritance tree, the problem would have remained when I've duplicated QtArModel. However, I can't find anything in my QtArModel that's class-scoped instead of instance-scoped.
What am I missing?
OK, I've managed to work this out. Apparently, the problem was not the inheritance, but the GC. Since the only connection to the models was from TableView's model property - which is just a wrapper for C++ getter and setter - ruby thought it lost the reference to my models, and GC'd them.
Solved by keeping the models in ruby variables.
I am building a search with the keywords cached in a table. Before a user-inputted keyword is looked up in the table, it is normalized. For example, some punctuation like '-' is removed and the casing is standardized. The normalized keyword is then used to find fetch the search results.
I am currently handling the normalization in the controller with a before_filter. I was wondering if there was a way to do this in the model instead. Something conceptually like a "before_find" callback would work although that wouldn't make sense on for an instance level.
You should be using named scopes:
class Whatever < ActiveRecord::Base
named_scope :search, lambda {|*keywords|
{:conditions => {:keyword => normalize_keywords(keywords)}}}
def self.normalize_keywords(keywords)
# Work your magic here
end
end
Using named scopes will allow you to chain with other scopes, and is really the way to go using Rails 3.
You probably don't want to implement this by overriding find. Overriding something like find will probably be a headache down the line.
You could create a class method that does what you need however, something like:
class MyTable < ActiveRecord::Base
def self.find_using_dirty_keywords(*args)
#Cleanup input
#Call to actual find
end
end
If you really want to overload find you can do it this way:
As an example:
class MyTable < ActiveRecord::Base
def self.find(*args)
#work your magic here
super(args,you,want,to,pass)
end
end
For more info on subclassing checkout this link: Ruby Tips
much like the above, you can also use an alias_method_chain.
class YourModel < ActiveRecord::Base
class << self
def find_with_condition_cleansing(*args)
#modify your args
find_without_condition_cleansing(*args)
end
alias_method_chain :find, :condition_cleansing
end
end