Rails開発日記

0.nil? #=> false
0.zero? #= true
0.empty? #=> NoMethodError
0.blank? #=> false
0 == false #=> false

"".nil? #=> false
"".zero? #=> NoMethodError
"".empty? #=> true
"".blank? #=> true
"" == false #=> false

{}.nil? #=> false
{}.zero? #=> NoMethodError
{}.empty? #=> true
{}.blank? #=> true
{} == false #=> false

[].nil? #=> false
[].zero? #=> NoMethodError
[].empty? #=> true
[].blank? #=> true
[] == false #=> false

nil.nil? #=> true
nil.zero? #=> NoMethodError
nil.empty? #=> NoMethodError
nil.blank? #=> true
nil == false #=> false

false.nil? #=> false
false.zero? #=> NoMethodError
false.empty? #=> NoMethodError
false.blank? #=> true
false == false #=> true

i = 0; i = 1 and i == 1
#=> true
i
#=> 1

i = 0; i = 1 && i == 1
#=> false
i
#=> false

優先順位が分かるように括弧をつけると。

i = 0; (i = 1) and (i == 1)
i = 0; i = (1 && (i == 1))

上の場合は、iには1がはりますが、下の場合には、iにfalseが入ります。

class User < ActiveRecord::Base
attr_protected :is_admin
end
user = User.new
user.attributes = {:username=>'Phusion', :is_admin=>true}
user.username # => "Phusion"
user.is_admin? # => false

user.send(:attributes=, {:username=>'Phusion',:is_admin=>true}, false)
user.is_admin? # => true

cnd = Condition.new
cnd.and('items.id', [1,2,3,4])
cnd.and do |c|
　c.or('items.start_at', 'is', nil)
　c.or('items.start_at', '<=', Time.now)
end
cnd.and('sql', 'exists (select * from liquors where iquors.item_id = items.id)')

SELECT * FROM items
WHERE (items.id IN (1,2,3,4)
　AND (items.start_at is NULL OR items.start_at <= '2009-09-08 10:54:42')
　AND exists (select * from liquors where iquors.item_id = items.id))

gem install mysql

PassengerHighPerformance on
PassengerMaxPoolSize 30
PassengerMaxInstancesPerApp 0
PassengerPoolIdleTime 300
PassengerMaxRequests 0

<VirtualHost *:80>
ServerName rails.sample.jp
DocumentRoot /path-to-rails/public
<Directory "/path-to-rails/public">
Options -Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
Allow from all
</Directory>

RailsAllowModRewrite on

RewriteEngine On

RewriteCond %{DOCUMENT_ROOT}/maintenance.html -f
RewriteCond %{REMOTE_ADDR} !^192\.168\.
RewriteRule . /maintenance.html [L]

RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
RewriteRule ^/(.*)$ /%{REQUEST_URI} [P,QSA,L]

ProxyRequests Off
ErrorLog "|/usr/sbin/rotatelogs /var/log/apache2/rails.sample.jp_error.log.%Y%m%d 86400 540"
LogLevel warn
CustomLog "|/usr/sbin/rotatelogs /var/log/apache2/rails.sample.jp_access.log.%Y%m%d 86400 540" combined
ServerSignature Off
</VirtualHost>

flash.now[:notice] = "リダイレクトしませんでした。"

<%= flash[:notice] %>

def User < ActiveRecord::Base
has_and_belongs_to_many :clubs, :join_table=>:club_members, :foreign_key=>:member_id
end
user = User.find(1)
user.club_ids = [11,12]
# INSERT INTO club_members(`club_id`) VALUES(11)
# INSERT INTO club_members(`club_id`) VALUES(12)
# member_idが入らない！

def User < ActiveRecord::Base
has_and_belongs_to_many :clubs, :join_table=>:club_members, :foreign_key=>"member_id"
end
user = User.find(1)
user.club_ids = [11,12]
# INSERT INTO club_members(`club_id`,`user_id`) VALUES(11,1)
# INSERT INTO club_members(`club_id`,`user_id`) VALUES(12,1)

class User < ActiveRecord::Base
def after_initialize
self.gender ||= "male"
end
end
User.find(1) # OK
Usre.find(1, :select=>"id,age") # ERROR
# ActiveRecord::MissingAttributeError: missing attribute: gender

class User < ActiveRecord::Base
def after_initialize
self.gender ||= "male" if self.has_attribude?(:gender)
end
end
User.find(1) # OK
Usre.find(1, :select=>"id,age") # OK
# ActiveRecord::MissingAttributeError: missing attribute: gender

1.2 - 1.0 == 0.2
=> false

1.2.to_d - 1.0.to_d == 0.2.to_d
=> true