Class: Object
Instance Attribute Summary
-
#blank? ⇒ true, false
readonly
An object is blank if it’s false, empty, or a whitespace string.
-
#duplicable? ⇒ Boolean
readonly
Can you safely dup this object?
- #html_safe? ⇒ Boolean readonly
-
#present? ⇒ true, false
readonly
An object is present if it’s not blank.
Instance Method Summary
-
#acts_like?(duck) ⇒ Boolean
Provides a way to check whether some class acts like some other class based on the existence of an appropriately-named marker method.
-
#deep_dup
Returns a deep copy of object if it’s duplicable.
-
#in?(another_object) ⇒ Boolean
Returns true if this object is included in the argument.
-
#instance_values
Returns a hash with string keys that maps instance variable names without “@” to their corresponding values.
-
#instance_variable_names
Returns an array of instance variable names as strings including “@”.
-
#presence ⇒ Object
Returns the receiver if it’s present otherwise returns
nil
. -
#presence_in(another_object) ⇒ Object
Returns the receiver if it’s included in the argument otherwise returns
nil
. -
#to_param
Alias of
to_s
. -
#to_query(key)
Converts an object into a string suitable for use as a URL query string, using the given
key
as the param name. -
#try(*args, &block)
Invokes the public method whose name goes as first argument just like
public_send
does, except that if the receiver does not respond to it the call returnsnil
rather than raising an exception. -
#try!(*args, &block)
Same as #try, but raises a
NoMethodError
exception if the receiver is notnil
and does not implement the tried method. -
#with(**attributes)
Set and restore public attributes around a block.
-
#with_options(options, &block)
An elegant way to factor duplication out of options passed to a series of method calls.
Instance Attribute Details
#blank? ⇒ true
, false
(readonly)
An object is blank if it’s false, empty, or a whitespace string. For example, nil
, ”, ‘ ’, [], {}, and false
are all blank.
This simplifies
!address || address.empty?
to
address.blank?
# File 'activesupport/lib/active_support/core_ext/object/blank.rb', line 18
def blank? respond_to?(:empty?) ? !!empty? : !self end
#duplicable? ⇒ Boolean
(readonly)
Can you safely dup this object?
False for method objects; true otherwise.
# File 'activesupport/lib/active_support/core_ext/object/duplicable.rb', line 26
def duplicable? true end
#html_safe? ⇒ Boolean
(readonly)
[ GitHub ]
# File 'activesupport/lib/active_support/core_ext/string/output_safety.rb', line 7
def html_safe? false end
#present? ⇒ true
, false
(readonly)
An object is present if it’s not blank.
# File 'activesupport/lib/active_support/core_ext/object/blank.rb', line 25
def present? !blank? end
Instance Method Details
#acts_like?(duck) ⇒ Boolean
Provides a way to check whether some class acts like some other class based on the existence of an appropriately-named marker method.
A class that provides the same interface as SomeClass
may define a marker method named acts_like_some_class?
to signal its compatibility to callers of acts_like?(:some_class)
.
For example, Active Support extends ::Date
to define an acts_like_date?
method, and extends ::Time
to define acts_like_time?
. As a result, developers can call x.acts_like?(:time)
and x.acts_like?(:date)
to test duck-type compatibility, and classes that are able to act like ::Time
can also define an acts_like_time?
method to interoperate.
Note that the marker method is only expected to exist. It isn’t called, so its body or return value are irrelevant.
Example: A class that provides the same interface as ::String
This class may define:
class Stringish
def acts_like_string?
end
end
Then client code can query for duck-type-safeness this way:
Stringish.new.acts_like?(:string) # => true
# File 'activesupport/lib/active_support/core_ext/object/acts_like.rb', line 33
def acts_like?(duck) case duck when :time respond_to? :acts_like_time? when :date respond_to? :acts_like_date? when :string respond_to? :acts_like_string? else respond_to? :"acts_like_#{duck}?" end end
#deep_dup
Returns a deep copy of object if it’s duplicable. If it’s not duplicable, returns self
.
object = Object.new
dup = object.deep_dup
dup.instance_variable_set(:@a, 1)
object.instance_variable_defined?(:@a) # => false
dup.instance_variable_defined?(:@a) # => true
# File 'activesupport/lib/active_support/core_ext/object/deep_dup.rb', line 15
def deep_dup duplicable? ? dup : self end
#in?(another_object) ⇒ Boolean
Returns true if this object is included in the argument.
When argument is a ::Range
, #cover?
is used to properly handle inclusion check within open ranges. Otherwise, argument must be any object which responds to #include?
. Usage:
characters = ["Konata", "Kagami", "Tsukasa"]
"Konata".in?(characters) # => true
For non ::Range
arguments, this will throw an ArgumentError
if the argument doesn’t respond to #include?
.
# File 'activesupport/lib/active_support/core_ext/object/inclusion.rb', line 15
def in?(another_object) case another_object when Range another_object.cover?(self) else another_object.include?(self) end rescue NoMethodError raise ArgumentError.new("The parameter passed to #in? must respond to #include?") end
#instance_values
Returns a hash with string keys that maps instance variable names without “@” to their corresponding values.
class C
def initialize(x, y)
@x, @y = x, y
end
end
C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}
# File 'activesupport/lib/active_support/core_ext/object/instance_variables.rb', line 14
def instance_values instance_variables.to_h do |ivar| [ivar[1..-1].freeze, instance_variable_get(ivar)] end end
#instance_variable_names
Returns an array of instance variable names as strings including “@”.
class C
def initialize(x, y)
@x, @y = x, y
end
end
C.new(0, 1).instance_variable_names # => ["@y", "@x"]
See additional method definition at line 30.
# File 'activesupport/lib/active_support/core_ext/object/instance_variables.rb', line 34
def instance_variable_names instance_variables.map(&:name) end
#presence ⇒ Object
Returns the receiver if it’s present otherwise returns nil
. object.presence
is equivalent to
object.present? ? object : nil
For example, something like
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 'activesupport/lib/active_support/core_ext/object/blank.rb', line 45
def presence self if present? end
#presence_in(another_object) ⇒ Object
Returns the receiver if it’s included in the argument otherwise returns nil
. Argument must be any object which responds to #include?
. Usage:
params[:bucket_type].presence_in %w( project calendar )
This will throw an ArgumentError
if the argument doesn’t respond to #include?
.
# File 'activesupport/lib/active_support/core_ext/object/inclusion.rb', line 34
def presence_in(another_object) in?(another_object) ? self : nil end
#to_param
Alias of to_s
.
# File 'activesupport/lib/active_support/core_ext/object/to_query.rb', line 7
def to_param to_s end
#to_query(key)
Converts an object into a string suitable for use as a URL query string, using the given key
as the param name.
#try(*args, &block)
Invokes the public method whose name goes as first argument just like public_send
does, except that if the receiver does not respond to it the call returns nil
rather than raising an exception.
This method is defined to be able to write
@person.try(:name)
instead of
@person.name if @person
try
calls can be chained:
@person.try(:spouse).try(:name)
instead of
@person.spouse.name if @person && @person.spouse
try
will also return nil
if the receiver does not respond to the method:
@person.try(:non_existing_method) # => nil
instead of
@person.non_existing_method if @person.respond_to?(:non_existing_method) # => nil
try
returns nil
when called on nil
regardless of whether it responds to the method:
nil.try(:to_i) # => nil, rather than 0
Arguments and blocks are forwarded to the method if invoked:
@posts.try(:each_slice, 2) do |a, b|
#...
end
The number of arguments in the signature must match. If the object responds to the method the call is attempted and ArgumentError
is still raised in case of argument mismatch.
If try
is called without arguments it yields the receiver to a given block unless it is nil
:
@person.try do |p|
#...
end
You can also call try with a block without accepting an argument, and the block will be instance_eval’ed instead:
@person.try { upcase.truncate(50) }
Please also note that try
is defined on Object
. Therefore, it won’t work with instances of classes that do not have Object
among their ancestors, like direct subclasses of BasicObject
.
# File 'activesupport/lib/active_support/core_ext/object/try.rb', line 39
rdoc_method :method: try
#try!(*args, &block)
Same as #try, but raises a NoMethodError
exception if the receiver is not nil
and does not implement the tried method.
"a".try!(:upcase) # => "A"
nil.try!(:upcase) # => nil
123.try!(:upcase) # => NoMethodError: undefined method `upcase' for 123:Integer
# File 'activesupport/lib/active_support/core_ext/object/try.rb', line 104
rdoc_method :method: try!
#with(**attributes)
Set and restore public attributes around a block.
client.timeout # => 5
client.with(timeout: 1) do
client.timeout # => 1
end
client.timeout # => 5
This method is a shorthand for the common begin/ensure pattern:
old_value = object.attribute
begin
object.attribute = new_value
# do things
ensure
object.attribute = old_value
end
It can be used on any object as long as both the reader and writer methods are public.
# File 'activesupport/lib/active_support/core_ext/object/with.rb', line 24
def with(**attributes) old_values = {} begin attributes.each do |key, value| old_values[key] = public_send(key) public_send("#{key}=", value) end yield ensure old_values.each do |key, old_value| public_send("#{key}=", old_value) end end end
#with_options(options, &block)
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
or ::Hash
-like object 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
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. locale: user.locale, scope: 'newsletter' do |i18n|
subject i18n.t :subject
body i18n.t :body, user_name: user.name
end
When you don’t pass an explicit receiver, it executes the whole block in merging options context:
class Account < ActiveRecord::Base
dependent: :destroy do
has_many :customers
has_many :products
has_many :invoices
has_many :expenses
end
end
with_options
can also be nested since the call is forwarded to its receiver.
NOTE: Each nesting level will merge inherited defaults in addition to their own.
class Post < ActiveRecord::Base
if: :persisted?, length: { minimum: 50 } do
validates :content, if: -> { content.present? }
end
end
The code is equivalent to:
validates :content, length: { minimum: 50 }, if: -> { content.present? }
Hence the inherited default for if
key is ignored.
NOTE: You cannot call class methods implicitly inside of with_options
. You can access these methods using the class name instead:
class Phone < ActiveRecord::Base
enum :phone_number_type, { home: 0, office: 1, mobile: 2 }
presence: true do
validates :phone_number_type, inclusion: { in: Phone.phone_number_types.keys }
end
end
When the block argument is omitted, the decorated Object
instance is returned:
module MyStyledHelpers
def styled
style: "color: red;"
end
end
styled.link_to "I'm red", "/"
# => <a href="/" style="color: red;">I'm red</a>
styled. "I'm red too!"
# => <button style="color: red;">I'm red too!</button>
# File 'activesupport/lib/active_support/core_ext/object/with_options.rb', line 92
def (, &block) option_merger = ActiveSupport::OptionMerger.new(self, ) if block block.arity.zero? ? option_merger.instance_eval(&block) : block.call(option_merger) else option_merger end end