diff options
-rw-r--r-- | activerecord/lib/active_record/associations.rb | 26 |
1 files changed, 14 insertions, 12 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb index 7ec7eb1b24..6ac457a2cd 100644 --- a/activerecord/lib/active_record/associations.rb +++ b/activerecord/lib/active_record/associations.rb @@ -447,9 +447,11 @@ module ActiveRecord # # Possible callbacks are: +before_add+, +after_add+, +before_remove+ and +after_remove+. # - # Should any of the +before_add+ callbacks throw an exception, the object does not get - # added to the collection. Same with the +before_remove+ callbacks; if an exception is - # thrown the object doesn't get removed. + # If any of the +before_add+ callbacks throw an exception, the object will not be + # added to the collection. + # + # Similarly, if any of the +before_remove+ callbacks throw an exception, the object + # will not be removed from the collection. # # == Association extensions # @@ -647,7 +649,7 @@ module ActiveRecord # belongs_to :commenter # end # - # When using nested association, you will not be able to modify the association because there + # When using a nested association, you will not be able to modify the association because there # is not enough information to know what modification to make. For example, if you tried to # add a <tt>Commenter</tt> in the example above, there would be no way to tell how to set up the # intermediate <tt>Post</tt> and <tt>Comment</tt> objects. @@ -717,7 +719,7 @@ module ActiveRecord # == Eager loading of associations # # Eager loading is a way to find objects of a certain class and a number of named associations. - # This is one of the easiest ways of to prevent the dreaded N+1 problem in which fetching 100 + # It is one of the easiest ways to prevent the dreaded N+1 problem in which fetching 100 # posts that each need to display their author triggers 101 database queries. Through the # use of eager loading, the number of queries will be reduced from 101 to 2. # @@ -749,16 +751,16 @@ module ActiveRecord # Post.includes(:author, :comments).each do |post| # # This will load all comments with a single query. This reduces the total number of queries - # to 3. More generally the number of queries will be 1 plus the number of associations + # to 3. In general, the number of queries will be 1 plus the number of associations # named (except if some of the associations are polymorphic +belongs_to+ - see below). # # To include a deep hierarchy of associations, use a hash: # - # Post.includes(:author, {comments: {author: :gravatar}}).each do |post| + # Post.includes(:author, { comments: { author: :gravatar } }).each do |post| # - # That'll grab not only all the comments but all their authors and gravatar pictures. - # You can mix and match symbols, arrays and hashes in any combination to describe the - # associations you want to load. + # The above code will load all the comments and all of their associated + # authors and gravatars. You can mix and match any combination of symbols, + # arrays, and hashes to retrieve the associations you want to load. # # All of this power shouldn't fool you into thinking that you can pull out huge amounts # of data with no performance penalty just because you've reduced the number of queries. @@ -767,8 +769,8 @@ module ActiveRecord # cut down on the number of queries in a situation as the one described above. # # Since only one table is loaded at a time, conditions or orders cannot reference tables - # other than the main one. If this is the case Active Record falls back to the previously - # used LEFT OUTER JOIN based strategy. For example + # other than the main one. If this is the case, Active Record falls back to the previously + # used LEFT OUTER JOIN based strategy. For example: # # Post.includes([:author, :comments]).where(['comments.approved = ?', true]) # |