Class: Object

### Home Classes Methods

### In Files

- lib/active_support/core_ext/kernel/agnostics.rb
- lib/active_support/core_ext/load_error.rb
- lib/active_support/core_ext/object/acts_like.rb
- lib/active_support/core_ext/object/blank.rb
- lib/active_support/core_ext/object/duplicable.rb
- lib/active_support/core_ext/object/instance_variables.rb
- lib/active_support/core_ext/object/returning.rb
- lib/active_support/core_ext/object/to_param.rb
- lib/active_support/core_ext/object/to_query.rb
- lib/active_support/core_ext/object/try.rb
- lib/active_support/core_ext/object/with_options.rb
- lib/active_support/core_ext/string/output_safety.rb
- lib/active_support/core_ext/uri.rb
- lib/active_support/hash_with_indifferent_access.rb
- lib/active_support/json/encoding.rb
- lib/active_support/xml_mini/jdom.rb

### Parent

BasicObject

### Namespace

- CLASS Object::HashWithIndifferentAccess
- CLASS Object::MissingSourceFile

### Methods

- #acts_like?
- #blank?
- #duplicable?
- #html_safe?
- #instance_variable_names
- #presence
- #present?
- #returning
- #to_param
- #to_query
- #try
- #unescape
- #with_options

### Included Modules

- Java

### Class/Module Index

Quicksearch

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No matching classes.

# Object

Most objects are cloneable, but not all. For example you can’t dup `nil`:

    nil.dup # => TypeError: can't dup NilClass

Classes may signal their instances are not duplicable removing `dup`/`clone` or raising exceptions from them. So, to dup an arbitrary object you normally use an optimistic approach and are ready to catch an exception, say:

    arbitrary_object.dup rescue object

Rails dups objects in a few critical spots where they are not that arbitrary. That rescue is very expensive (like 40 times slower than a predicate), and it is often triggered.

That’s why we hardcode the following cases and check duplicable? instead of using that rescue idiom.

### Constants

HashWithIndifferentAccess
MissingSourceFile

### Public Instance Methods

acts_like?(duck) click to toggle source

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

blank?() click to toggle source

An object is blank if it’s false, empty, or a whitespace string. For example, “”, “ ”, `nil`, [], and {} are blank.

This simplifies:

    if !address.nil? && !address.empty?

…to:

    if !address.blank?

    # File lib/active_support/core_ext/object/blank.rb, line 12
    def blank?
      respond_to?(:empty?) ? empty? : !self
    end

duplicable?() click to toggle source

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 20
    def duplicable?
      true
    end

html_safe?() click to toggle source

    # File lib/active_support/core_ext/string/output_safety.rb, line 63
    def html_safe?
      false
    end

instance_variable_names() click to toggle source

    # File lib/active_support/core_ext/object/instance_variables.rb, line 30
    def instance_variable_names
      instance_variables.map { |var| var.to_s }
    end

presence() click to toggle source

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 35
    def presence
      self if present?
    end

present?() click to toggle source

An object is present if it’s not blank.

    # File lib/active_support/core_ext/object/blank.rb, line 17
    def present?
      !blank?
    end

returning(value) click to toggle source

Returns `value` after yielding `value` to the block. This simplifies the process of constructing an object, performing work on the object, and then returning the object from a method. It is a Ruby-ized realization of the K combinator, courtesy of Mikael Brockman.

#### Examples

    # Without returning
    def foo
      values = []
      values << "bar"
      values << "baz"
      return values
    end

    foo # => ['bar', 'baz']

    # returning with a local variable
    def foo
      returning values = [] do
        values << 'bar'
        values << 'baz'
      end
    end

    foo # => ['bar', 'baz']

    # returning with a block argument
    def foo
      returning [] do |values|
        values << 'bar'
        values << 'baz'
      end
    end

    foo # => ['bar', 'baz']

    # File lib/active_support/core_ext/object/returning.rb, line 38
    def returning(value)
      ActiveSupport::Deprecation.warn('Object#returning has been deprecated in favor of Object#tap.', caller)
      yield(value)
      value
    end

to_param() click to toggle source

Alias of `to_s`.

    # File lib/active_support/core_ext/object/to_param.rb, line 5
    def to_param
      to_s
    end

to_query(key) click to toggle source

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_s).gsub(/%(5B|5D)/n) { [$1].pack('H*') }}=#{CGI.escape(to_param.to_s)}"
    end

try(method, *args, &block) click to toggle source

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.

#### Examples

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}

    # File lib/active_support/core_ext/object/try.rb, line 25
    def try(method, *args, &block)
      send(method, *args, &block)
    end

unescape(str, escaped = /%[a-fA-F\d]{2}/) click to toggle source

    # 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

with_options(options) click to toggle source

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.

    with_options :order => 'created_at', :class_name => 'Comment' do |post|
      post.has_many :comments, :conditions => ['approved = ?', true], :dependent => :delete_all
      post.has_many :unapproved_comments, :conditions => ['approved = ?', false]
      post.has_many :all_comments
    end

Can also be used with an explicit receiver:

    map.with_options :controller => "people" do |people|
      people.connect "/people",     :action => "index"
      people.connect "/people/:id", :action => "show"
    end

    # File lib/active_support/core_ext/object/with_options.rb, line 23
    def with_options(options)
      yield ActiveSupport::OptionMerger.new(self, options)
    end

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