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 7: def acts_like?(duck) 8: respond_to? :"acts_like_#{duck}?" 9: 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 15 15: def blank? 16: respond_to?(:empty?) ? empty? : !self 17: 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 24: def duplicable? 25: true 26: end
# File lib/active_support/core_ext/string/output_safety.rb, line 76 76: def html_safe? 77: false 78: end
Returns true if this object is included in the argument(s). Argument must be any object which responds to # 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 #.
# File lib/active_support/core_ext/object/inclusion.rb, line 13 13: def in?(*args) 14: if args.length > 1 15: args.include? self 16: else 17: another_object = args.first 18: if another_object.respond_to? :include? 19: another_object.include? self 20: else 21: raise ArgumentError.new("The single parameter passed to #in? must respond to #include?") 22: end 23: end 24: end
# File lib/active_support/core_ext/object/instance_variables.rb, line 27 27: def instance_variable_names 28: instance_variables.map { |var| var.to_s } 29: 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 38 38: def presence 39: self if present? 40: end
An object is present if it’s not blank?.
# File lib/active_support/core_ext/object/blank.rb, line 20 20: def present? 21: !blank? 22: 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 15: def to_json(options = nil) 16: ActiveSupport::JSON.encode(self, options) 17: end
Alias of to_s.
# File lib/active_support/core_ext/object/to_param.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.
# File lib/active_support/core_ext/object/to_query.rb, line 8 8: def to_query(key) 9: require 'cgi' unless defined?(CGI) && defined?(CGI::escape) 10: "#{CGI.escape(key.to_param)}=#{CGI.escape(to_param.to_s)}" 11: 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 32: def try(*a, &b) 33: if a.empty? && block_given? 34: yield self 35: else 36: __send__(*a, &b) 37: end 38: end
# File lib/active_support/core_ext/uri.rb, line 13 13: def unescape(str, escaped = /%[a-fA-F\d]{2}/) 14: # TODO: Are we actually sure that ASCII == UTF-8? 15: # YK: My initial experiments say yes, but let's be sure please 16: enc = str.encoding 17: enc = Encoding::UTF_8 if enc == Encoding::US_ASCII 18: str.gsub(escaped) { [$&[1, 2].hex].pack('C') }.force_encoding(enc) 19: 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 40: def with_options(options) 41: yield ActiveSupport::OptionMerger.new(self, options) 42: end
Disabled; run with --debug to generate this.
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