Class: Object

Inherits:
BasicObject
Includes:
InstanceExecMethods
Defined in:
lib/passive_support/core_ext/object/misc.rb,
lib/passive_support/core_ext/object/blank.rb,
lib/passive_support/core_ext/kernel/agnostics.rb,
lib/passive_support/core_ext/object/extending.rb,
lib/passive_support/core_ext/object/conversions.rb,
lib/passive_support/core_ext/object/singleton_class.rb,
lib/passive_support/core_ext/object/instance_variables.rb

Defined Under Namespace

Modules: InstanceExecMethods

Instance Method Summary collapse

Instance Method Details

#`(command) ⇒ Object

Makes backticks behave (somewhat more) similarly on all platforms. On win32 ‘nonexistent_command` raises Errno::ENOENT; on Unix, the spawned shell prints a message to stderr and sets $?. We emulate Unix on the former but not the latter.



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# File 'lib/passive_support/core_ext/kernel/agnostics.rb', line 6

def `(command) #:nodoc:
  super
rescue Errno::ENOENT => e
  STDERR.puts "#$0: #{e}"
end

#acts_like?(duck) ⇒ Boolean

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.

Returns:

  • (Boolean) 


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# File 'lib/passive_support/core_ext/object/misc.rb', line 86

def acts_like?(duck)
  respond_to? "acts_like_#{duck}?"
end

#blank? ⇒ Boolean

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?

Returns:

  • (Boolean) 


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# File 'lib/passive_support/core_ext/object/blank.rb', line 12

def blank?
  respond_to?(:empty?) ? empty? : !self
end

#class_eval(*args, &block) ⇒ Object

class_eval on an object acts like singleton_class_eval.



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# File 'lib/passive_support/core_ext/object/singleton_class.rb', line 10

def class_eval(*args, &block)
  singleton_class.class_eval(*args, &block)
end

#copy_instance_variables_from(object, exclude = []) ⇒ Object

Copies the instance variables of object into self.

Instance variable names in the exclude array are ignored. If object responds to protected_instance_variables the ones returned are also ignored. For example, Rails controllers implement that method.

In both cases strings and symbols are understood, and they have to include the at sign.

class C
  def initialize(x, y, z)
    @x, @y, @z = x, y, z
  end

  def protected_instance_variables
    %w(@z)
  end
end

a = C.new(0, 1, 2)
b = C.new(3, 4, 5)

a.copy_instance_variables_from(b, [:@y])
# a is now: @x = 3, @y = 1, @z = 2



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# File 'lib/passive_support/core_ext/object/instance_variables.rb', line 68

def copy_instance_variables_from(object, exclude = []) #:nodoc:
  exclude += object.protected_instance_variables if object.respond_to? :protected_instance_variables

  vars = object.instance_variables.map(&:to_s) - exclude.map(&:to_s)
  vars.each { |name| instance_variable_set(name, object.instance_variable_get(name)) }
end

#extend_with_included_modules_from(object) ⇒ Object

:nodoc:



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# File 'lib/passive_support/core_ext/object/extending.rb', line 50

def extend_with_included_modules_from(object) #:nodoc:
  object.extended_by.each { |mod| extend mod }
end

#extended_by ⇒ Object

:nodoc:



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# File 'lib/passive_support/core_ext/object/extending.rb', line 45

def extended_by #:nodoc:
  ancestors = class << self; ancestors end
  ancestors.select { |mod| mod.class == Module } - [ Object, Kernel ]
end

#instance_exec(*args, &block) ⇒ Object

Evaluate the block with the given arguments within the context of this object, so self is set to the method receiver.

From Mauricio’s eigenclass.org/hiki/bounded+space+instance_exec



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# File 'lib/passive_support/core_ext/object/extending.rb', line 63

def instance_exec(*args, &block)
  begin
    old_critical, Thread.critical = Thread.critical, true
    n = 0
    n += 1 while respond_to?(method_name = "__instance_exec#{n}")
    InstanceExecMethods.module_eval { define_method(method_name, &block) }
  ensure
    Thread.critical = old_critical
  end

  begin
    send(method_name, *args)
  ensure
    InstanceExecMethods.module_eval { remove_method(method_name) } rescue nil
  end
end

#instance_values ⇒ Object

Returns a hash that maps instance variable names without “@” to their corresponding values. Keys are strings both in Ruby 1.8 and 1.9.

class C
  def initialize(x, y)
    @x, @y = x, y
  end
end

C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}



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# File 'lib/passive_support/core_ext/object/instance_variables.rb', line 19

def instance_values #:nodoc:
  instance_variables.inject({}) do |values, name|
    values[name.to_s[1..-1]] = instance_variable_get(name)
    values
  end
end

#instance_variable_defined?(variable) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/passive_support/core_ext/object/instance_variables.rb', line 4

def instance_variable_defined?(variable)
  instance_variables.include?(variable.to_s)
end

#presence ⇒ Object

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'



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# File 'lib/passive_support/core_ext/object/blank.rb', line 35

def presence
  self if present?
end

#present? ⇒ Boolean

An object is present if it’s not blank.

Returns:

  • (Boolean) 


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# File 'lib/passive_support/core_ext/object/blank.rb', line 17

def present?
  !blank?
end

#remove_subclasses_of(*superclasses) ⇒ Object

:nodoc:



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# File 'lib/passive_support/core_ext/object/extending.rb', line 2

def remove_subclasses_of(*superclasses) #:nodoc:
  Class.remove_class(*subclasses_of(*superclasses))
end

#returning(value) {|value| ... } ⇒ Object

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']

Yields:

  • (value) 


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# File 'lib/passive_support/core_ext/object/misc.rb', line 38

def returning(value)
  yield(value)
  value
end

#singleton_class ⇒ Object

Returns the object’s singleton class.



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# File 'lib/passive_support/core_ext/object/singleton_class.rb', line 3

def singleton_class
  class << self
    self
  end
end

#tap {|_self| ... } ⇒ Object

Yields x to the block, and then returns x. The primary purpose of this method is to “tap into” a method chain, in order to perform operations on intermediate results within the chain.

(1..10).tap { |x| puts "original: #{x.inspect}" }.to_a.
  tap    { |x| puts "array: #{x.inspect}" }.
  select { |x| x%2 == 0 }.
  tap    { |x| puts "evens: #{x.inspect}" }.
  map    { |x| x*x }.
  tap    { |x| puts "squares: #{x.inspect}" }

Yields:

  • (_self)

Yield Parameters:

  • _self (Object) —

    the object that the method was called on



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# File 'lib/passive_support/core_ext/object/misc.rb', line 53

def tap
  yield self
  self
end

#to_param ⇒ Object

Alias of to_s.



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# File 'lib/passive_support/core_ext/object/conversions.rb', line 3

def to_param
  to_s
end

#to_query(key) ⇒ Object

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.



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# File 'lib/passive_support/core_ext/object/conversions.rb', line 11

def to_query(key)
  require 'cgi' unless defined?(CGI) && defined?(CGI::escape)
  "#{CGI.escape(key.to_s)}=#{CGI.escape(to_param.to_s)}"
end

#with_options(options) {|ActiveSupport::OptionMerger.new(self, options)| ... } ⇒ Object

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

Yields:

  • (ActiveSupport::OptionMerger.new(self, options)) 


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# File 'lib/passive_support/core_ext/object/misc.rb', line 77

def with_options(options)
  yield ActiveSupport::OptionMerger.new(self, options)
end