- acts_like?
- as_json
- blank?
- class_eval
- duplicable?
- html_safe?
- instance_exec
- instance_variable_defined?
- instance_variable_names
- lookup_missing_generator
- metaclass
- presence
- present?
- returning
- singleton_class
- tap
- to_json
- to_param
- to_param
- to_query
- try
- with_options
- InstanceExecMethods
Lookup missing generators using const_missing. This allows any generator to reference another without having to know its location: RubyGems, ~/.rails/generators, and RAILS_ROOT/generators.
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# File railties/lib/rails_generator/lookup.rb, line 10 10: def lookup_missing_generator(class_id) 11: if md = /(.+)Generator$/.match(class_id.to_s) 12: name = md.captures.first.demodulize.underscore 13: Rails::Generator::Base.lookup(name).klass 14: else 15: const_missing_before_generators(class_id) 16: end 17: end
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.
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# File activesupport/lib/active_support/core_ext/object/misc.rb, line 86 86: def acts_like?(duck) 87: respond_to? "acts_like_#{duck}?" 88: end
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# File activesupport/lib/active_support/json/encoders/object.rb, line 7 7: def as_json(options = nil) 8: instance_values 9: end
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?
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# File activesupport/lib/active_support/core_ext/object/blank.rb, line 12 12: def blank? 13: respond_to?(:empty?) ? empty? : !self 14: end
class_eval on an object acts like singleton_class_eval.
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# File activesupport/lib/active_support/core_ext/object/singleton_class.rb, line 10 10: def class_eval(*args, &block) 11: singleton_class.class_eval(*args, &block) 12: end
Can you safely .dup this object? False for nil, false, true, symbols, and numbers; true otherwise.
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# File activesupport/lib/active_support/core_ext/duplicable.rb, line 4 4: def duplicable? 5: true 6: end
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# File activesupport/lib/active_support/core_ext/string/output_safety.rb, line 52 52: def html_safe? 53: false 54: end
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 activesupport/lib/active_support/core_ext/object/extending.rb, line 63 63: def instance_exec(*args, &block) 64: begin 65: old_critical, Thread.critical = Thread.critical, true 66: n = 0 67: n += 1 while respond_to?(method_name = "__instance_exec#{n}") 68: InstanceExecMethods.module_eval { define_method(method_name, &block) } 69: ensure 70: Thread.critical = old_critical 71: end 72: 73: begin 74: send(method_name, *args) 75: ensure 76: InstanceExecMethods.module_eval { remove_method(method_name) } rescue nil 77: end 78: end
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# File activesupport/lib/active_support/core_ext/object/instance_variables.rb, line 4 4: def instance_variable_defined?(variable) 5: instance_variables.include?(variable.to_s) 6: end
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# File activesupport/lib/active_support/core_ext/object/instance_variables.rb, line 37 37: def instance_variable_names 38: instance_variables.map { |var| var.to_s } 39: end
Get object‘s meta (ghost, eigenclass, singleton) class.
Deprecated in favor of Object#singleton_class.
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# File activesupport/lib/active_support/core_ext/object/metaclass.rb, line 7 7: def metaclass 8: class << self 9: self 10: end 11: 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'
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# File activesupport/lib/active_support/core_ext/object/blank.rb, line 35 35: def presence 36: self if present? 37: end
An object is present if it‘s not blank.
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# File activesupport/lib/active_support/core_ext/object/blank.rb, line 17 17: def present? 18: !blank? 19: end
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']
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# File activesupport/lib/active_support/core_ext/object/misc.rb, line 38 38: def returning(value) 39: yield(value) 40: value 41: end
Returns the object‘s singleton class.
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# File activesupport/lib/active_support/core_ext/object/singleton_class.rb, line 3 3: def singleton_class 4: class << self 5: self 6: end 7: end
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}" }
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# File activesupport/lib/active_support/core_ext/object/misc.rb, line 53 53: def tap 54: yield self 55: self 56: end
Dumps object in JSON (JavaScript Object Notation). See www.json.org for more info.
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# File activesupport/lib/active_support/json/encoders/object.rb, line 3 3: def to_json(options = nil) 4: ActiveSupport::JSON.encode(as_json(options)) 5: end
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# File actionpack/lib/action_controller/routing/routing_ext.rb, line 2 2: def to_param 3: to_s 4: end
Alias of to_s.
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# File activesupport/lib/active_support/core_ext/object/conversions.rb, line 3 3: def to_param 4: to_s 5: 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.
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# File activesupport/lib/active_support/core_ext/object/conversions.rb, line 11 11: def to_query(key) 12: require 'cgi' unless defined?(CGI) && defined?(CGI::escape) 13: "#{CGI.escape(key.to_s)}=#{CGI.escape(to_param.to_s)}" 14: 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.
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}
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# File activesupport/lib/active_support/core_ext/try.rb, line 25 25: def try(method, *args, &block) 26: send(method, *args, &block) 27: 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.
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
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# File activesupport/lib/active_support/core_ext/object/misc.rb, line 77 77: def with_options(options) 78: yield ActiveSupport::OptionMerger.new(self, options) 79: end