.nil?
can be used on any object and is true if the object is nil.
.empty?
can be used on strings, arrays and hashes and returns true if:
- String length == 0
- Array length == 0
- Hash length == 0
Running .empty?
on something that is nil will throw a NoMethodError
.
That is where .blank?
comes in. It is implemented by Rails and will operate on any object as well as work like .empty?
on strings, arrays and hashes.
nil.blank? == true
false.blank? == true
[].blank? == true
{}.blank? == true
"".blank? == true
5.blank? == false
0.blank? == false
.blank?
also evaluates true on strings which are non-empty but contain only whitespace:
" ".blank? == true
" ".empty? == false
Rails also provides .present?
, which returns the negation of .blank?
.
Array gotcha: blank?
will return false
even if all elements of an array are blank. To determine blankness in this case, use all?
with blank?
, for example:
[ nil, '' ].blank? == false
[ nil, '' ].all? &:blank? == true
rename_column :table, :old_column, :new_column
You'll probably want to create a separate migration to do this. (Rename FixColumnName
as you will.):
script/generate migration FixColumnName
# creates db/migrate/xxxxxxxxxx_fix_column_name.rb
Then edit the migration to do your will:
# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
def self.up
rename_column :table_name, :old_column, :new_column
end
def self.down
# rename back if you need or do something else or do nothing
end
end
For Rails 3.1 use:
While, the up
and down
methods still apply, Rails 3.1 receives a change
method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".
See "Active Record Migrations" for more information.
rails g migration FixColumnName
class FixColumnName < ActiveRecord::Migration
def change
rename_column :table_name, :old_column, :new_column
end
end
If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:
rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...
You could use change_table
to keep things a little neater:
class FixColumnNames < ActiveRecord::Migration
def change
change_table :table_name do |t|
t.rename :old_column1, :new_column1
t.rename :old_column2, :new_column2
...
end
end
end
Then just db:migrate
as usual or however you go about your business.
For Rails 4:
While creating a Migration
for renaming a column, Rails 4 generates a change
method instead of up
and down
as mentioned in the above section. The generated change
method is:
$ > rails g migration ChangeColumnName
which will create a migration file similar to:
class ChangeColumnName < ActiveRecord::Migration
def change
rename_column :table_name, :old_column, :new_column
end
end
Best Answer
You have to do like this:
Read this guide to understand what mass-assignment is: http://guides.rubyonrails.org/security.html
I am wondering why do have to directly set the encrypted password. You could do this: