From ccc89f4899b1f251ebc20ad0d6a96c448da69f01 Mon Sep 17 00:00:00 2001 From: Xavier Noria Date: Thu, 12 Aug 2010 00:15:29 +0200 Subject: AS guide: some revisions --- .../source/active_support_core_extensions.textile | 50 ++++++++-------------- 1 file changed, 17 insertions(+), 33 deletions(-) diff --git a/railties/guides/source/active_support_core_extensions.textile b/railties/guides/source/active_support_core_extensions.textile index 54f766fffd..8ccfc8e304 100644 --- a/railties/guides/source/active_support_core_extensions.textile +++ b/railties/guides/source/active_support_core_extensions.textile @@ -1,8 +1,10 @@ h2. Active Support Core Extensions -Active Support is the Rails component responsible for providing Ruby language extensions, utilities, and other transversal stuff. It offers a richer bottom-line at the language level, targeted both at the development of Rails applications, and at the development of Rails itself. +Active Support is the Ruby on Rails component responsible for providing Ruby language extensions, utilities, and other transversal stuff. -By referring to this guide you will learn the extensions to the Ruby core classes and modules provided by Rails. +It offers a richer bottom-line at the language level, targeted both at the development of Rails applications, and at the development of Ruby on Rails itself. + +By referring to this guide you will learn the extensions to the Ruby core classes and modules provided by Active Support. endprologue. @@ -84,32 +86,25 @@ The following values are considered to be blank in a Rails application: WARNING: Note that numbers are not mentioned, in particular 0 and 0.0 are *not* blank. -For example, this method from +ActionDispatch::Response+ uses +blank?+ to easily be robust to +nil+ and whitespace strings in one shot: +For example, this method from +ActionDispatch::Session::AbstractStore+ uses +blank?+ for checking whether a session key is present: -def charset - charset = String(headers["Content-Type"] || headers["type"]).split(";")[1] - charset.blank? ? nil : charset.strip.split("=")[1] +def ensure_session_key! + if @key.blank? + raise ArgumentError, 'A key is required...' + end end -That's a typical use case for +blank?+. - -Here, the method Rails runs to instantiate observers upon initialization has nothing to do if there are none: +The method +present?+ is equivalent to +!blank?+. This example is taken from +ActionDispatch::Http::Cache::Response+: -def instantiate_observers - return if @observers.blank? - # ... +def set_conditional_cache_control! + return if self["Cache-Control"].present? + ... end -The method +present?+ is equivalent to +!blank?+: - - -assert @response.body.present? # same as !@response.body.blank? - - NOTE: Defined in +active_support/core_ext/object/blank.rb+. h4. +presence+ @@ -151,28 +146,17 @@ Active Support provides +duplicable?+ to programmatically query an object about false.duplicable? # => false -By definition all objects are +duplicable?+ except +nil+, +false+, +true+, symbols, numbers, and class objects. +By definition all objects are +duplicable?+ except +nil+, +false+, +true+, symbols, numbers, and class and module objects. -WARNING. Using +duplicable?+ is discouraged because it depends on a hard-coded list. Classes have means to disallow duplication like removing +dup+ and +clone+ or raising exceptions from them, only +rescue+ can tell. +WARNING. Any class can disallow duplication removing +dup+ and +clone+ or raising exceptions from them, only +rescue+ can tell whether a given arbitrary object is duplicable. +duplicable?+ depends on the hard-coded list above, but it is much faster than +rescue+. Use it only if you know the hard-coded list is enough in your use case. NOTE: Defined in +active_support/core_ext/object/duplicable.rb+. h4. +try+ -Sometimes you want to call a method provided the receiver object is not +nil+, which is something you usually check first. - -For instance, note how this method of +ActiveRecord::ConnectionAdapters::AbstractAdapter+ checks if there's a +@logger+: - - -def log_info(sql, name, ms) - if @logger && @logger.debug? - name = '%s (%.1fms)' % [name || 'SQL', ms] - @logger.debug(format_log_entry(name, sql.squeeze(' '))) - end -end - +Sometimes you want to call a method provided the receiver object is not +nil+, which is something you usually check first. +try+ is like +Object#send+ except that it returns +nil+ if sent to +nil+. -You can shorten that using +Object#try+. This method is a synonym for +Object#send+ except that it returns +nil+ if sent to +nil+. The previous example could then be rewritten as: +For instance, in this code from +ActiveRecord::ConnectionAdapters::AbstractAdapter+ +@logger+ could be +nil+, but you save the check and write in an optimistic style: def log_info(sql, name, ms) -- cgit v1.2.3