A duck-type assistant method. For example, Active Support extends Date to define an acts_like_date? method, and extends Time to define acts_like_time?. As a result, we can do “x.acts_like?(:time)” and “x.acts_like?(:date)” to do duck-type-safe comparisons, since classes that we want to act like Time simply need to define an acts_like_time? method.
# File lib/active_support/core_ext/object/acts_like.rb, line 7 def acts_like?(duck) respond_to? :"acts_like_#{duck}?" end
An object is blank if it's false, empty, or a whitespace string. For
example, “”, “ ”, nil
, [], and {} are all blank.
This simplifies:
if address.nil? || address.empty?
…to:
if address.blank?
# File lib/active_support/core_ext/object/blank.rb, line 14 def blank? respond_to?(:empty?) ? empty? : !self end
Can you safely dup this object?
False for nil
, false
, true
, symbols,
numbers, class and module objects; true otherwise.
# File lib/active_support/core_ext/object/duplicable.rb, line 24 def duplicable? true end
# File lib/active_support/core_ext/string/output_safety.rb, line 76 def html_safe? false end
Returns true if this object is included in the argument(s). Argument must
be any object which responds to #include?
or optionally,
multiple arguments can be passed in. Usage:
characters = ["Konata", "Kagami", "Tsukasa"] "Konata".in?(characters) # => true character = "Konata" character.in?("Konata", "Kagami", "Tsukasa") # => true
This will throw an ArgumentError if a single argument is passed in and it
doesn't respond to #include?
.
# File lib/active_support/core_ext/object/inclusion.rb, line 13 def in?(*args) if args.length > 1 args.include? self else another_object = args.first if another_object.respond_to? :include? another_object.include? self else raise ArgumentError.new("The single parameter passed to #in? must respond to #include?") end end end
# File lib/active_support/core_ext/object/instance_variables.rb, line 27 def instance_variable_names instance_variables.map { |var| var.to_s } end
Returns object if it's present?
otherwise returns
nil
. object.presence
is equivalent to
object.present? ? object : nil
.
This is handy for any representation of objects where blank is the same as not present at all. For example, this simplifies a common check for HTTP POST/query parameters:
state = params[:state] if params[:state].present? country = params[:country] if params[:country].present? region = state || country || 'US'
…becomes:
region = params[:state].presence || params[:country].presence || 'US'
# File lib/active_support/core_ext/object/blank.rb, line 37 def presence self if present? end
An object is present if it's not blank?
.
# File lib/active_support/core_ext/object/blank.rb, line 19 def present? !blank? end
Dumps object in JSON (JavaScript Object Notation). See www.json.org for more info.
# File lib/active_support/core_ext/object/to_json.rb, line 15 def to_json(options = nil) ActiveSupport::JSON.encode(self, options) end
Alias of to_s
.
# File lib/active_support/core_ext/object/to_param.rb, line 3 def to_param to_s end
Converts an object into a string suitable for use as a URL query string,
using the given key
as the param name.
Note: This method is defined as a default implementation for all Objects for Hash#to_query to work.
# File lib/active_support/core_ext/object/to_query.rb, line 8 def to_query(key) require 'cgi' unless defined?(CGI) && defined?(CGI::escape) "#{CGI.escape(key.to_param)}=#{CGI.escape(to_param.to_s)}" end
Invokes the method identified by the symbol method
, passing it
any arguments and/or the block specified, just like the regular Ruby
Object#send
does.
Unlike that method however, a NoMethodError
exception will not be raised and nil
will be
returned instead, if the receiving object is a nil
object or
NilClass.
If try is called without a method to call, it will yield any given block with the object.
Please also note that try
is defined on Object
,
therefore it won't work with subclasses of BasicObject
.
For example, using try with SimpleDelegator
will delegate
try
to target instead of calling it on delegator itself.
Without try
@person && @person.name
or
@person ? @person.name : nil
With try
@person.try(:name)
try
also accepts arguments and/or a block, for the method it
is trying
Person.try(:find, 1) @people.try(:collect) {|p| p.name}
Without a method argument try will yield to the block unless the receiver is nil.
@person.try { |p| "#{p.first_name} #{p.last_name}" }
# File lib/active_support/core_ext/object/try.rb, line 32 def try(*a, &b) if a.empty? && block_given? yield self else __send__(*a, &b) end end
# File lib/active_support/core_ext/uri.rb, line 12 def unescape(str, escaped = /%[a-fA-F\d]{2}/) # TODO: Are we actually sure that ASCII == UTF-8? # YK: My initial experiments say yes, but let's be sure please enc = str.encoding enc = Encoding::UTF_8 if enc == Encoding::US_ASCII str.gsub(escaped) { [$&[1, 2].hex].pack('C') }.force_encoding(enc) end
An elegant way to factor duplication out of options passed to a series of
method calls. Each method called in the block, with the block variable as
the receiver, will have its options merged with the default
options
hash provided. Each method called on the block
variable must take an options hash as its final argument.
Without with_options>
, this code contains duplication:
class Account < ActiveRecord::Base has_many :customers, :dependent => :destroy has_many :products, :dependent => :destroy has_many :invoices, :dependent => :destroy has_many :expenses, :dependent => :destroy end
Using with_options
, we can remove the duplication:
class Account < ActiveRecord::Base with_options :dependent => :destroy do |assoc| assoc.has_many :customers assoc.has_many :products assoc.has_many :invoices assoc.has_many :expenses end end
It can also be used with an explicit receiver:
I18n.with_options :locale => user.locale, :scope => "newsletter" do |i18n| subject i18n.t :subject body i18n.t :body, :user_name => user.name end
with_options
can also be nested since the call is forwarded to
its receiver. Each nesting level will merge inherited defaults in addition
to their own.
# File lib/active_support/core_ext/object/with_options.rb, line 40 def with_options(options) yield ActiveSupport::OptionMerger.new(self, options) end