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Available options are (none of these exists by default):
* :limit - Requests a maximum column length. This is number of characters for :string and :text columns and number of bytes for :binary and :integer columns. * :default - The column‘s default value. Use nil for NULL. * :null - Allows or disallows NULL values in the column. This option could have been named :null_allowed. * :precision - Specifies the precision for a :decimal column. * :scale - Specifies the scale for a :decimal column.
Pretty Printing Routes
if you’d like to check out your routes in the console, you can do something like:
routes = ActionController::Routing::Routes
# which will return a RouteSet puts routes.routes
which’ll give you a nice output like: GET /messages/ {:action=>“index”, :controller=>“messages”} GET /messages.:format/ {:action=>“index”, :controller=>“messages”} POST /messages/ {:action=>“create”, :controller=>“messages”} POST /messages.:format/ {:action=>“create”, :controller=>“messages”} GET /messages/new/ {:action=>“new”, :controller=>“messages”} GET /messages/new.:format/ {:action=>“new”, :controller=>“messages”} GET /messages/:id/edit/ {:action=>“edit”, :controller=>“messages”} GET /messages/:id/edit.:format/ {:action=>“edit”, :controller=>“messages”} GET /messages/:id/ {:action=>“show”, :controller=>“messages”} GET /messages/:id.:format/ {:action=>“show”, :controller=>“messages”} PUT /messages/:id/ {:action=>“update”, :controller=>“messages”} PUT /messages/:id.:format/ {:action=>“update”, :controller=>“messages”} DELETE /messages/:id/ {:action=>“destroy”, :controller=>“messages”} DELETE /messages/:id.:format/ {:action=>“destroy”, :controller=>“messages”}
To verify if the element exists before replacing.
Just add this code into a initializer file.
Atention: The code starts at the “module ActionView” and the last “end” has to be copied too.
module ActionView
module Helpers module PrototypeHelper class JavaScriptGenerator #:nodoc: module GeneratorMethods def replace_html_if_exists(id, *options_for_render) call "if($('#{id}')) Element.update", id, render(*options_for_render) end end end end end
end
Be careful with name of attribute writer
If restricting access to attributes you normally get code like
attr_accessible :foo,
When using these nested attributes you end up with code like
attr_accessible :foo, :bar_attributes
Its very easy to leave of the _attributes suffix e.g
attr_accessible :foo, :bar
which will cause you all sorts of problems
:selected
If you want some object to be selected by default, be sure to use its id, not the whole object.
collection_select(:post, :author_id, Author.all, :id, :name_with_initial, {:selected => current_book.authors.map(&:id)}) #=> :selected => [1,2,3,4]
and not
collection_select(:post, :author_id, Author.all, :id, :name_with_initial, {:selected => current_book.authors})
Returns a copy of the attribute contents
As szeryf notes, this is a really expensive method, but another important remark is that the contents returned are a copy of the actual values.
model.attributes['name'] # => 'Joe' model.attributes['name'] = 'Jim' model.attributes['name'] # => 'Joe' still model.name # => 'Joe'
This has the potential to be confusing as you’re given the impression you have direct access to the attributes.
Antonym of empty?
The antonym of empty? is Enumerable#any? method:
[].empty? #=> true [].any? #=> false [1].empty? #=> false [1].any? #=> true
Be cautious however, if your array might contain nil’s or false’s:
[false, nil].any? #=> false
Validate() is run always before one of the more specific validation methods
I did not see this mentioned explicitly anywhere.
The method validate is run always before a call to validate_on_create or validate_on_update is made.
Example:
class Foo < ActiveRecord::Base def validate puts 'In validate' end def validate_on_create puts 'In validate_on_create' end def validate_on_update puts 'In validate_on_update' end end
Now, when creating a new Foo using script/console, the output is as follows:
In validate In validate_on_create
and when updating a Foo, the output looks like:
In validate In validate_on_update
Optional local assigns
When you have a partial with optional local assigns, for instance:
<%= render :partial => 'articles/preview' %> <%= render :partial => 'articles/preview', :locals => { :show_call_out => true } %>
And you don’t want the partial to break when the local isn’t assigned, you can reference it through the local_assigns local variable instead of through the template binding:
<% if local_assigns[:show_call_out] %> <em><%= format @article.call_out %></em> <% end %>
Usage example
class Aa
class_inheritable_accessor :test end => [:test] Aa.test = 10 => 10 Aa.test => 10 Bb = Class.new(Aa) => Bb Bb.test => 10 Bb.test = 5 => 5 Bb.test => 5 Aa.test => 10
Re: How to test different responses
In addition to using:
@request.accept = "text/javascript" #=> request JS
as rubymaverick and nachocab suggested, you can also pass :format when calling your action, eg:
it "GET #most_viewed renders #most_viewed.js.rjs template if js requested" do get :most_viewed, :format => 'js' response.should render_template('most_viewed') end
Not really deprecated
This isn’t really deprecated, it’s just relocated to ActiveRecord::AttributeMethods#read_attribute
Important note
It has been said that “it can be compared to, but isn’t the same thing as”:
class Bar class << self attr_accessor :greeting end end
Which is true. However, they are “inherited” isn’t exactly the case. Rather, cattr_accessor uses class variables.
The problem with class variables in Ruby, is that a class variable is the same object across all subclasses of a class. Consider the following example of what happens with cattr_accessor:
class A @@foo = 'foo' def self.foo @@foo end end p A.foo # => "foo" class B < A end p B.foo # => "foo" class B @@foo = 'bar' end p B.foo # => "bar"
So far so good you might think. However, something you might not have expected is that the variable has now also changed in class A:
p A.foo # => "bar"
This is in my opinion almost never what you’d want. More probable is that you’d want the individual class instance to have an accessor. (Remember classes are objects in Ruby). I do the following in regular Ruby:
class A class << self attr_accessor :foo end self.foo = 'foo' end p A.foo # => "foo" class B < A end p B.foo # => nil class B self.foo = 'bar' end p B.foo # => "bar" p A.foo # => "foo"
As you can see, this returns nil when a value hasn’t explicitly been set yet on the new class instance. If you’d like to have inheritance without messing with the superclasses variables, have a look at ActiveSupport’s class_inheritable_accessor, which does the same as I just explained, but creates a clone of the object and assigns it to the subclass whenever a class is inherited.
What I’d normally do in Ruby to fix the issue of it returning nil is to create the accessor manually and have it set the instance variable to the default if it’s nil:
class A class << self def foo @foo ||= 'foo' end end end class B < A end p B.foo # => nil
So to recap:
-
cattr_accessor uses class variables (@@foo), in which case the object is shared across all subclasses of a class. Use it mainly for static data, in which case you’d probably best use a constant.
-
class_inheritable_accessor (or what I showed) uses instance variables (@foo) at the Class instance level. These variables are not shared across all subclasses.
Expensive method!
This method builds the a new hash every time it’s called, so be cautious not to use it in loops etc.
Skipping validation
Unlike the save method, you can’t pass false to update_attributes to tell it to skip validation. Should you wish to do this (consider carefully if this is wise) update the attributes explicitly then call save and pass false:
@model_name.attributes = params[:model_name] @model_name.save false
:discard_month implicitly sets :discard_day to true
This may not be the behaviour that you want, and setting :discard_day => false doesn’t change this. One way of getting around this is to hide the month field using CSS e.g.
#some_date_field_2i { display:none; }
If you use the :default option for the date_select, the correct default month will be passed through to the controller. Using this with :discard_year will give you a dropdown with only the day, but preserve the month and year as provided by :default.
Requirements for extra parameters not working
nm. just delete this entry
cattr_accessor_with_default
Class attribute assessors are neat if you want to set up modifiable constant-like varibles. This is how you’d normally set it up:
module MyPlugin class Conf @@awesome_level = 'huge' cattr_accessor :awesome_level end end
Then you can call and modify it like this:
>> MyPlugin::Conf.awesome_level => 'huge' >> MyPlugin::Conf.awesome_level = 'massive' >> MyPlugin::Conf.awesome_level => 'massive'
If you have a pile of those accessors I’d do something like this (there might be a better way, but it works):
module MyPlugin class Conf def self.cattr_accessor_with_default(name, value = nil) cattr_accessor name self.send("#{name}=", value) if value end cattr_accessor_with_default :awesome_level, 'huge' cattr_accessor_with_default :speed_level, 'insane' cattr_accessor_with_default :indifferent_level cattr_accessor_with_default :craziness_level, 'nuts' end end
This way you declare accessor and it’s optional default value on the same line
A stub with argument and return value
it “should use a dummy method with argument and return value” do
dummy = mock("dummy").stub!(:emulate) dummy.should_receive(:emulate).with(:something).and_return("Done! sir!") dummy.emulate(:something).should == "Done! sir!" end
Conditions work for lower-level validate methods too
I don’t think this is mentioned in the docs anywhere, or else I couldn’t find it: Because validate, validate_on_create, and validate_on_update are ActiveSupport::Callbacks, their symbol forms support conditions just like validates_presence_of and company:
validate :permaname_must_be_unique, :if => :normal_entry? validate_on_create :posted_at_must_be_valid_timestamp, :unless => Proc.new {|e| e.posted_at.nil? } validate_on_update :title_must_not_contain_apostrophes, :if => :title_starts_with_a_b?
Not really helpful
When you’re trying to construct a specialized path name for a partial based on a record type you’re probably better off writing your own helper.
def topic_partial_path(topic) ['admin', topic.class.table_name, "#{topic.class.table_name.singularize}_as_topic"].join('/') end
Keeping the flash object on multiple redirects
If your controllers are redirecting more than once, the flash contents will be lost. To avoid it, execute flash.keep before each redirection.
Check ActionController::Flash::FlashHash for more handy methods (discard, now, …)
How to use with exclusive scope
Code example
Article.with_exclusive_scope { find(:all) } #=> "SELECT * FROM 'articles'
from http://ryandaigle.com/articles/2008/11/18/what-s-new-in-edge-rails-default-scoping
list of predefined variables
$! The exception information message set by ‘raise’. $@ Array of backtrace of the last exception thrown.
$& The string matched by the last successful pattern match in this scope. $` The string to the left of the last successful match. $‘ The string to the right of the last successful match. $+ The last bracket matched by the last successful match. $1 to $9 The Nth group of the last successful regexp match. $~ The information about the last match in the current scope.
$= The flag for case insensitive, nil by default. $/ The input record separator, newline by default. $\ The output record separator for the print and IO#write. Default is nil. $, The output field separator for the print and Array#join. $; The default separator for String#split.
$. The current input line number of the last file that was read. $< The virtual concatenation file of the files given on command line. $> The default output for print, printf. $stdout by default. $_ The last input line of string by gets or readline.
$0 Contains the name of the script being executed. May be assignable. $* Command line arguments given for the script sans args. $$ The process number of the Ruby running this script. $? The status of the last executed child process. $: Load path for scripts and binary modules by load or require.
$“ The array contains the module names loaded by require. $DEBUG The status of the -d switch. $FILENAME Current input file from $<. Same as $<.filename. $LOAD_PATH The alias to the $:. $stderr The current standard error output. $stdin The current standard input. $stdout The current standard output. $VERBOSE The verbose flag, which is set by the -v switch. $-0 The alias to $/. $-a True if option -a (”autosplit“ mode) is set. Read-only variable. $-d The alias to $DEBUG. $-F The alias to $;. $-i If in-place-edit mode is set, this variable holds the extension, otherwise nil. $-I The alias to $:. $-l True if option -l is set (”line-ending processing“ is on). Read-only variable. $-p True if option -p is set (”loop“ mode is on). Read-only variable. $-v The alias to $VERBOSE. $-w True if option -w is set.
Source: http://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Variables_and_Constants#Pre-defined_Variables
Have the check_box checked by default
To have the check box checked by default, pass either :checked => true or :checked => 'checked' in the options. See ActionView::Helpers::InstanceTag#to_check_box_tag for details.