A convenience wrapper for find(:all, *args). You can pass in all the same arguments to this method as you can to find(:all).
# File lib/active_record/relation/finder_methods.rb, line 142 142: def all(*args) 143: args.any? ? apply_finder_options(args.first).to_a : to_a 144: end
Returns true if a record exists in the table that matches the id or conditions given, or false otherwise. The argument can take five forms:
Integer - Finds the record with this primary key.
String - Finds the record with a primary key corresponding to this string (such as '5').
Array - Finds the record that matches these find-style conditions (such as ['color = ?', 'red']).
Hash - Finds the record that matches these find-style conditions (such as {:color => 'red'}).
No args - Returns false if the table is empty, true otherwise.
For more information about specifying conditions as a Hash or Array, see the Conditions section in the introduction to ActiveRecord::Base.
Note: You can’t pass in a condition as a string (like name = 'Jamie'), since it would be sanitized and then queried against the primary key column, like id = 'name = 'Jamie''.
Person.exists?(5) Person.exists?('5') Person.exists?(:name => "David") Person.exists?(['name LIKE ?', "%#{query}%"]) Person.exists?
# File lib/active_record/relation/finder_methods.rb, line 171 171: def exists?(id = nil) 172: id = id.id if ActiveRecord::Base === id 173: 174: case id 175: when Array, Hash 176: where(id).exists? 177: else 178: relation = select(primary_key).limit(1) 179: relation = relation.where(primary_key.eq(id)) if id 180: relation.first ? true : false 181: end 182: end
Find operates with four different retrieval approaches:
Find by id - This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]). If no record can be found for all of the listed ids, then RecordNotFound will be raised.
Find first - This will return the first record matched by the options used. These options can either be specific conditions or merely an order. If no record can be matched, nil is returned. Use Model.find(:first, *args) or its shortcut Model.first(*args).
Find last - This will return the last record matched by the options used. These options can either be specific conditions or merely an order. If no record can be matched, nil is returned. Use Model.find(:last, *args) or its shortcut Model.last(*args).
Find all - This will return all the records matched by the options used. If no records are found, an empty array is returned. Use Model.find(:all, *args) or its shortcut Model.all(*args).
All approaches accept an options hash as their last parameter.
:conditions - An SQL fragment like “administrator = 1”, [ "user_name = ?", username ], or ["user_name = :user_name", { :user_name => user_name }]. See conditions in the intro.
:order - An SQL fragment like “created_at DESC, name”.
:group - An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
:having - Combined with :group this can be used to filter the records that a GROUP BY returns. Uses the HAVING SQL-clause.
:limit - An integer determining the limit on the number of rows that should be returned.
:offset - An integer determining the offset from where the rows should be fetched. So at 5, it would skip rows 0 through 4.
:joins - Either an SQL fragment for additional joins like “LEFT JOIN comments ON comments.post_id = id” (rarely needed), named associations in the same form used for the :include option, which will perform an INNER JOIN on the associated table(s), or an array containing a mixture of both strings and named associations. If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table’s columns. Pass :readonly => false to override.
:include - Names associations that should be loaded alongside. The symbols named refer to already defined associations. See eager loading under Associations.
:select - By default, this is “*” as in “SELECT * FROM”, but can be changed if you, for example, want to do a join but not include the joined columns. Takes a string with the SELECT SQL fragment (e.g. “id, name”).
:from - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name of a database view).
:readonly - Mark the returned records read-only so they cannot be saved or updated.
:lock - An SQL fragment like “FOR UPDATE” or “LOCK IN SHARE MODE”. :lock => true gives connection’s default exclusive lock, usually “FOR UPDATE”.
# find by id Person.find(1) # returns the object for ID = 1 Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6) Person.find([7, 17]) # returns an array for objects with IDs in (7, 17) Person.find([1]) # returns an array for the object with ID = 1 Person.find(1, :conditions => "administrator = 1", :order => "created_on DESC")
Note that returned records may not be in the same order as the ids you provide since database rows are unordered. Give an explicit :order to ensure the results are sorted.
# find first Person.find(:first) # returns the first object fetched by SELECT * FROM people Person.find(:first, :conditions => [ "user_name = ?", user_name]) Person.find(:first, :conditions => [ "user_name = :u", { :u => user_name }]) Person.find(:first, :order => "created_on DESC", :offset => 5) # find last Person.find(:last) # returns the last object fetched by SELECT * FROM people Person.find(:last, :conditions => [ "user_name = ?", user_name]) Person.find(:last, :order => "created_on DESC", :offset => 5) # find all Person.find(:all) # returns an array of objects for all the rows fetched by SELECT * FROM people Person.find(:all, :conditions => [ "category IN (?)", categories], :limit => 50) Person.find(:all, :conditions => { :friends => ["Bob", "Steve", "Fred"] } Person.find(:all, :offset => 10, :limit => 10) Person.find(:all, :include => [ :account, :friends ]) Person.find(:all, :group => "category")
Example for find with a lock: Imagine two concurrent transactions: each will read person.visits == 2, add 1 to it, and save, resulting in two saves of person.visits = 3. By locking the row, the second transaction has to wait until the first is finished; we get the expected person.visits == 4.
Person.transaction do person = Person.find(1, :lock => true) person.visits += 1 person.save! end
# File lib/active_record/relation/finder_methods.rb, line 95 95: def find(*args) 96: return to_a.find { |*block_args| yield(*block_args) } if block_given? 97: 98: options = args.extract_options! 99: 100: if options.present? 101: apply_finder_options(options).find(*args) 102: else 103: case args.first 104: when :first, :last, :all 105: send(args.first) 106: else 107: find_with_ids(*args) 108: end 109: end 110: end
A convenience wrapper for find(:first, *args). You can pass in all the same arguments to this method as you can to find(:first).
# File lib/active_record/relation/finder_methods.rb, line 114 114: def first(*args) 115: if args.any? 116: if args.first.kind_of?(Integer) || (loaded? && !args.first.kind_of?(Hash)) 117: to_a.first(*args) 118: else 119: apply_finder_options(args.first).first 120: end 121: else 122: find_first 123: end 124: end
A convenience wrapper for find(:last, *args). You can pass in all the same arguments to this method as you can to find(:last).
# File lib/active_record/relation/finder_methods.rb, line 128 128: def last(*args) 129: if args.any? 130: if args.first.kind_of?(Integer) || (loaded? && !args.first.kind_of?(Hash)) 131: to_a.last(*args) 132: else 133: apply_finder_options(args.first).last 134: end 135: else 136: find_last 137: end 138: end
# File lib/active_record/relation/finder_methods.rb, line 207 207: def apply_join_dependency(relation, join_dependency) 208: for association in join_dependency.join_associations 209: relation = association.join_relation(relation) 210: end 211: 212: limitable_reflections = using_limitable_reflections?(join_dependency.reflections) 213: 214: if !limitable_reflections && relation.limit_value 215: limited_id_condition = construct_limited_ids_condition(relation.except(:select)) 216: relation = relation.where(limited_id_condition) 217: end 218: 219: relation = relation.except(:limit, :offset) unless limitable_reflections 220: 221: relation 222: end
# File lib/active_record/relation/finder_methods.rb, line 345 345: def column_aliases(join_dependency) 346: join_dependency.joins.collect{|join| join.column_names_with_alias.collect{|column_name, aliased_name| 347: "#{connection.quote_table_name join.aliased_table_name}.#{connection.quote_column_name column_name} AS #{aliased_name}"}}.flatten.join(", ") 348: end
# File lib/active_record/relation/finder_methods.rb, line 224 224: def construct_limited_ids_condition(relation) 225: orders = relation.order_values.join(", ") 226: values = @klass.connection.distinct("#{@klass.connection.quote_table_name @klass.table_name}.#{@klass.primary_key}", orders) 227: 228: ids_array = relation.select(values).collect {|row| row[@klass.primary_key]} 229: ids_array.empty? ? raise(ThrowResult) : primary_key.in(ids_array) 230: end
# File lib/active_record/relation/finder_methods.rb, line 195 195: def construct_relation_for_association_calculations 196: including = (@eager_load_values + @includes_values).uniq 197: join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(@klass, including, arel.joins(arel)) 198: relation = except(:includes, :eager_load, :preload) 199: apply_join_dependency(relation, join_dependency) 200: end
# File lib/active_record/relation/finder_methods.rb, line 202 202: def construct_relation_for_association_find(join_dependency) 203: relation = except(:includes, :eager_load, :preload, :select).select(column_aliases(join_dependency)) 204: apply_join_dependency(relation, join_dependency) 205: end
# File lib/active_record/relation/finder_methods.rb, line 232 232: def find_by_attributes(match, attributes, *args) 233: conditions = attributes.inject({}) {|h, a| h[a] = args[attributes.index(a)]; h} 234: result = where(conditions).send(match.finder) 235: 236: if match.bang? && result.blank? 237: raise RecordNotFound, "Couldn't find #{@klass.name} with #{conditions.to_a.collect {|p| p.join(' = ')}.join(', ')}" 238: else 239: result 240: end 241: end
# File lib/active_record/relation/finder_methods.rb, line 329 329: def find_first 330: if loaded? 331: @records.first 332: else 333: @first ||= limit(1).to_a[0] 334: end 335: end
# File lib/active_record/relation/finder_methods.rb, line 337 337: def find_last 338: if loaded? 339: @records.last 340: else 341: @last ||= reverse_order.limit(1).to_a[0] 342: end 343: end
# File lib/active_record/relation/finder_methods.rb, line 288 288: def find_one(id) 289: id = id.id if ActiveRecord::Base === id 290: 291: record = where(primary_key.eq(id)).first 292: 293: unless record 294: conditions = arel.wheres.map { |x| x.value }.join(', ') 295: conditions = " [WHERE #{conditions}]" if conditions.present? 296: raise RecordNotFound, "Couldn't find #{@klass.name} with ID=#{id}#{conditions}" 297: end 298: 299: record 300: end
# File lib/active_record/relation/finder_methods.rb, line 243 243: def find_or_instantiator_by_attributes(match, attributes, *args) 244: protected_attributes_for_create, unprotected_attributes_for_create = {}, {} 245: args.each_with_index do |arg, i| 246: if arg.is_a?(Hash) 247: protected_attributes_for_create = args[i].with_indifferent_access 248: else 249: unprotected_attributes_for_create[attributes[i]] = args[i] 250: end 251: end 252: 253: conditions = (protected_attributes_for_create.merge(unprotected_attributes_for_create)).slice(*attributes).symbolize_keys 254: 255: record = where(conditions).first 256: 257: unless record 258: record = @klass.new do |r| 259: r.send(:attributes=, protected_attributes_for_create, true) unless protected_attributes_for_create.empty? 260: r.send(:attributes=, unprotected_attributes_for_create, false) unless unprotected_attributes_for_create.empty? 261: end 262: yield(record) if block_given? 263: record.save if match.instantiator == :create 264: end 265: 266: record 267: end
# File lib/active_record/relation/finder_methods.rb, line 302 302: def find_some(ids) 303: result = where(primary_key.in(ids)).all 304: 305: expected_size = 306: if @limit_value && ids.size > @limit_value 307: @limit_value 308: else 309: ids.size 310: end 311: 312: # 11 ids with limit 3, offset 9 should give 2 results. 313: if @offset_value && (ids.size - @offset_value < expected_size) 314: expected_size = ids.size - @offset_value 315: end 316: 317: if result.size == expected_size 318: result 319: else 320: conditions = arel.wheres.map { |x| x.value }.join(', ') 321: conditions = " [WHERE #{conditions}]" if conditions.present? 322: 323: error = "Couldn't find all #{@klass.name.pluralize} with IDs " 324: error << "(#{ids.join(", ")})#{conditions} (found #{result.size} results, but was looking for #{expected_size})" 325: raise RecordNotFound, error 326: end 327: end
# File lib/active_record/relation/finder_methods.rb, line 186 186: def find_with_associations 187: including = (@eager_load_values + @includes_values).uniq 188: join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(@klass, including, nil) 189: rows = construct_relation_for_association_find(join_dependency).to_a 190: join_dependency.instantiate(rows) 191: rescue ThrowResult 192: [] 193: end
# File lib/active_record/relation/finder_methods.rb, line 269 269: def find_with_ids(*ids) 270: return to_a.find { |*block_args| yield(*block_args) } if block_given? 271: 272: expects_array = ids.first.kind_of?(Array) 273: return ids.first if expects_array && ids.first.empty? 274: 275: ids = ids.flatten.compact.uniq 276: 277: case ids.size 278: when 0 279: raise RecordNotFound, "Couldn't find #{@klass.name} without an ID" 280: when 1 281: result = find_one(ids.first) 282: expects_array ? [ result ] : result 283: else 284: find_some(ids) 285: end 286: end
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