\u65b0\u5e74\u3067\u3059\u306d\u3002\u4e0b\u689d\u3067\u3059\u3002\u5e74\u672b\u30bf\u30a4\u306b\u6765\u3066\u3001\u73fe\u5728\u306f\u30d0\u30f3\u30b3\u30af\u3067\u50cd\u3044\u3066\u304a\u308a\u307e\u3057\u3066\u3001\u4eca\u9031\u672b\u65e5\u672c\u306b\u5e30\u308b\u4e88\u5b9a\u3067\u3059\u3002\u30d0\u30f3\u30b3\u30af\u306b\u7740\u3044\u305f\u306e\u306f\u660e\u3051\u65b9\u524d\u3067\u3001\u30bf\u30af\u30b7\u30fc\u3067\u4e45\u3057\u3076\u308a\u306b\u30dc\u30e9\u30ec\u3066\u3057\u307e\u3044\u307e\u3057\u305f\u3002\u96c6\u4e2d\u529b\u304c\u6b20\u3051\u3066\u308b\u6df1\u591c\u3053\u305d\u6c17\u3092\u629c\u3044\u3066\u306f\u3044\u3051\u306a\u3044\u306a\u3042\u3068\u601d\u3063\u305f\u6b21\u7b2c\u3067\u3059\u3002<\/p>\n
\u6280\u8853\u7684\u306a\u9762\u3067\u306f\u3001\u4e3b\u306bRuby on Rails\u3067\u306eWeb\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3001API\u958b\u767a\u3001\u305d\u3057\u3066\u5c11\u3057Android\u30a2\u30d7\u30ea\u958b\u767a\u306b\u643a\u308f\u3063\u305f\u3002\u3082\u3068\u3082\u3068\u306fC\u3001C++\u3001C#\u306a\u3069\u3067\u30df\u30c9\u30eb\u30a6\u30a7\u30a2\u3092\u958b\u767a\u3057\u3066\u304d\u305f\u751f\u7c8b\u306e\u30a8\u30f3\u30d7\u30e9\u4eba\u9593\u3060\u3063\u305f\u79c1\u3060\u3063\u305f\u304c\u3001\u3060\u3044\u3076Web\u4eba\u9593\u306b\u5909\u308f\u3063\u3066\u304d\u305f\u6c17\u304c\u3059\u308b\u3002\u3044\u3044\u610f\u5473\u3067\u5909\u308f\u3063\u305f\u306e\u306a\u3089\u3044\u3044\u306e\u3060\u304c\u3002<\/p>\n
\u307e\u305f\u3001\u4f1a\u793e\u306e\u30e1\u30f3\u30d0\u30fc\u3082\u5897\u3048\u3066\u304d\u305f\u3002\u5f0a\u793e\u306f\u57fa\u672c\u7684\u306b\u5b8c\u5168\u30ea\u30e2\u30fc\u30c8\u30ef\u30fc\u30af\u3067\u3042\u308b\u306e\u3067\u3001\u30e1\u30f3\u30d0\u30fc\u304c\u5897\u3048\u3066\u304d\u305f\u5834\u5408\u306b\u3069\u3046\u306a\u308b\u306e\u304b\u3044\u308d\u3044\u308d\u697d\u3057\u307f\u3067\u3042\u308b\u3002\u304a\u305d\u3089\u304f\u3001\u3044\u308d\u3044\u308d\u3068\u3084\u308a\u65b9\u3092\u5909\u3048\u3066\u3044\u304b\u306a\u3044\u3068\u3044\u3051\u306a\u3044\u3068\u601d\u3046\u304c\u3001\u305d\u3046\u3044\u3063\u305f\u5909\u5316\u3092\u697d\u3057\u307f\u306a\u304c\u3089\u67d4\u8edf\u306b\u3084\u3063\u3066\u3044\u304d\u305f\u3044\u3068\u8003\u3048\u3066\u3044\u308b\u3002<\/p>\n
\u305d\u3057\u3066\u3053\u308c\u306f\u500b\u4eba\u7684\u306a\u8a71\u3060\u304c\u3001\u5148\u6708\u306b\u8da3\u5473\u3067\u4f5c\u3063\u305f\u521d\u306eiOS\u30a2\u30d7\u30ea\u3092Apple\u306b\u7533\u8acb\u3057\u305f\u3002\u30a2\u30d7\u30ea\u3078\u306e\u30c7\u30fc\u30bf\u914d\u4fe1\u7528API\u30b5\u30fc\u30d0\u306fRails\u3067\u30a2\u30d7\u30ea\u3092\u4f5c\u3063\u3066DigitalOcean\u3092\u4f7f\u3063\u3066\u7acb\u3066\u305f\u3002DigitalOcean\u306fRails\u30a2\u30d7\u30ea\u306e\u30d5\u30a1\u30a4\u30eb\u3092\u30b3\u30d4\u30fc\u3059\u308b\u3060\u3051\u3067\u3059\u3050\u306b\u30b5\u30fc\u30d3\u30b9\u3092\u52d5\u304b\u305b\u308b\u3057\u5b89\u3044\u306e\u3067\u3001\u6642\u3068\u5834\u5408\u306b\u3088\u3063\u3066\u306f\u975e\u5e38\u306b\u4fbf\u5229\u3067\u3042\u308b\u3002\u5927\u5909\u306b\u898b\u305f\u76ee\u304c\u3057\u3087\u307c\u3044\uff08\u6a5f\u80fd\u306f\u7d20\u6674\u3089\u3057\u3044\u3068\u601d\u3063\u3066\u3044\u308b\uff09\u30a2\u30d7\u30ea\u306a\u306e\u3060\u304c\u3001\u3068\u308a\u3042\u3048\u305a\u5be9\u67fb\u306b\u51fa\u3057\u3066\u307f\u3066\u53cd\u5fdc\u3092\u898b\u3088\u3046\u3068\u601d\u3063\u3066\u51fa\u3057\u305f\u3068\u3053\u308d\u3001\u77ac\u6bba\u30ea\u30b8\u30a7\u30af\u30c8\u3055\u308c\u3066\u3057\u307e\u3063\u305f\u3002\u51ac\u4f11\u307f\u306b\u4fee\u6b63\u7248\u3092\u51fa\u3057\u305f\u306e\u3067\u3001\u79c1\u500b\u4eba\u306e\u521diOS\u30a2\u30d7\u30ea\u304c\u30ea\u30ea\u30fc\u30b9\u3055\u308c\u308b\u306e\u304c\u697d\u3057\u307f\u306a\u4eca\u65e5\u3053\u306e\u9803\u3067\u3042\u308b\u3002<\/p>\n
\u4eca\u5e74\u306fRuby on Rails\u306e\u30b9\u30ad\u30eb\u3092\u4f38\u3070\u3057\u3064\u3064\u3001\u30d5\u30eb\u30b9\u30bf\u30c3\u30af\u30a8\u30f3\u30b8\u30cb\u30a2\u3092\u76ee\u6307\u3059\u3079\u304f\uff1f\uff1f\uff1f\uff1f\uff1f\u7a4d\u6975\u7684\u306b\u30b9\u30de\u30fc\u30c8\u30d5\u30a9\u30f3\u3084Web\u30af\u30e9\u30a4\u30a2\u30f3\u30c8\u30b5\u30a4\u30c9\u306e\u958b\u767a\u306b\u3082\u95a2\u308f\u3063\u3066\u3044\u304d\u305f\u3044\u3068\u601d\u3063\u3066\u3044\u308b\u3002\u4ed6\u306b\u3082\u3001\u524d\u8077\u3067\u3084\u3063\u3066\u304d\u305fJava\u3084.NET\u306f\u4e00\u5fdc\u5f97\u610f\u5206\u91ce\u3067\u3042\u308b\u306e\u3067\u3001\u305d\u3053\u3089\u3078\u3093\u306e\u53d7\u8a17\u6848\u4ef6\u3092\u3044\u305f\u3060\u3051\u3070\u305c\u3072\u5168\u529b\u3067\u53d6\u308a\u7d44\u307f\u305f\u3044\u3068\u8003\u3048\u3066\u3044\u308b\u3002<\/p>\n
\u3055\u3066\u672c\u984c\u3067\u3042\u308b\u304c\u3001\u65b0\u5e74\u3063\u307d\u304f\u306a\u3044\u5730\u5473\u306a\u30cd\u30bf\u3068\u306a\u3063\u3066\u3057\u307e\u3046\u304c\u3001Rails\u306eActiveRecord\u3067\u6700\u8fd1\u3061\u3087\u3063\u3068\u30cf\u30de\u3063\u305f\u5c0f\u7c92\u30cd\u30bf\u30922\u3064\u66f8\u3053\u3046\u3068\u601d\u3046\u3002<\/p>\n
Rails\u3001MySQL\u306e\u30d0\u30fc\u30b8\u30e7\u30f3\u306f\u4ee5\u4e0b\u3002<\/p>\n
\u6700\u8fd1\u4f5c\u308a\u3053\u3093\u3060\u30d0\u30b0\u306e\u304a\u8a71\u3002<\/p>\n
ActiveRecord\u306efind_by\u30e1\u30bd\u30c3\u30c9\u306b\u4e3b\u30ad\u30fc\u3092\u6e21\u3057\u3066\u30e2\u30c7\u30eb\u3092\u691c\u7d22\u3057\u3088\u3046\u3068\u3057\u305f\u969b\u3001\u672c\u6765\u30cf\u30c3\u30b7\u30e5\u3092\u6e21\u3059\u3079\u304d\u3068\u3053\u308d\u3067\u3001\u8aa4\u3063\u3066\u4e3b\u30ad\u30fc\u306e\u5024\u306e\u307f\u3092\u6e21\u3057\u3066\u3044\u305f\u30b3\u30fc\u30c9\u304c\u3042\u3063\u305f\u3002<\/p>\n
SomeModel.create(id: 1, some_column: 'hoge')\nSomeModel.create(id: 2, some_column: 'fuga')\nSomeModel.find_by(id: 2)\u3000\u2192\u6b63\u3057\u3044\u30b3\u30fc\u30c9\n=> #<SomeModel id: 2, some_column: "fuga">\nSomeModel.find_by(2)\u3000\u2192\u4eca\u56de\u66f8\u3044\u3066\u3057\u307e\u3063\u3066\u3044\u305f\u30d0\u30b0\u3063\u3066\u308b\u30b3\u30fc\u30c9\n=> #<SomeModel id: 1, some_column: "hoge"><\/code><\/pre>\n\u975e\u5e38\u306b\u5358\u7d14\u306a\u30d0\u30b0\u306a\u306e\u3060\u304c\u3001\u3001\u3001
\n\u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u3067\u691c\u51fa\u3067\u304d\u305a\u3001\u767a\u898b\u304c\u9045\u308c\u305f\u3002
\n\u4e0a\u8a18\u306e\u4f8b\u3067\u306f\u3001find_by(id: 2)\u304cid\uff1a2\u306e\u30ec\u30b3\u30fc\u30c9\u3092\u8fd4\u3057\u3066\u3044\u308b\u306e\u306b\u5bfe\u3057\u3001find_by(2)\u306f\u30a8\u30e9\u30fc\u3068\u306f\u306a\u3089\u305a\u3001id\uff1a1\u306e\u30ec\u30b3\u30fc\u30c9\u3092\u8fd4\u3057\u3066\u3044\u308b\u3002<\/p>\n
SomeModel.find_by(2)\u3067\u767a\u884c\u3055\u308c\u308bSQL\u3092\u898b\u3066\u307f\u308b\u3068\u3001<\/p>\n
SomeModel Load (0.3ms) SELECT "some_models".* FROM "some_models" WHERE (2) LIMIT 1<\/code><\/pre>\n\u3053\u308c\u306f\u5f53\u7136\u306a\u304c\u3089\u610f\u56f3\u3057\u305f\u30af\u30a8\u30ea\u3067\u306f\u306a\u3044\u3002\u3057\u304b\u3057\u3001\u30a8\u30e9\u30fc\u3068\u306a\u3089\u305a\u306b\u7d50\u679c\u304c\u8fd4\u3063\u3066\u304f\u308b\u3002\u305d\u3057\u3066\u3001\u4e3b\u30ad\u30fc\u304c'2'\u306e\u30ec\u30b3\u30fc\u30c9\u3067\u306f\u306a\u304f\u3001\u5168\u4ef6\u5f15\u3063\u304b\u304b\u3063\u305f\u4e2d\u306eLIMIT 1\u3067\u4e00\u756a\u6700\u521d\u306e\u30ec\u30b3\u30fc\u30c9\u304c\u8fd4\u3063\u3066\u304f\u308b\u3002<\/p>\n
\u30a8\u30e9\u30fc\u306b\u306a\u3089\u305a\u306b\u7d50\u679c\u304c\u3061\u3083\u3093\u30681\u4ef6\u8fd4\u3063\u3066\u304f\u308b\u3068\u3044\u3046\u306e\u304c\u3061\u3087\u3063\u3068\u3044\u3084\u3089\u3057\u304f\u3066\u3001\u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u306f\u901a\u3063\u3066\u3057\u307e\u3063\u3066\u3044\u305f\u3002\u3068\u3044\u3046\u306e\u3082\u3001\u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u3067\u306f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\uff08\u30ec\u30b3\u30fc\u30c9\uff09\u3092\u3072\u3068\u3064\u3057\u304b\u4f5c\u3063\u3066\u304a\u3089\u305a\u3001find_by\u30e1\u30bd\u30c3\u30c9\u306b\u8aa4\u3063\u305f\u5f15\u6570\u3092\u4e0e\u3048\u3066\u3044\u3066\u3082\u610f\u56f3\u305b\u305a\u306b\u6b63\u3057\u3044\u30ec\u30b3\u30fc\u30c9\u304c\u5f15\u3051\u3066\u3057\u307e\u3063\u3066\u3044\u305f\u305f\u3081\u3067\u3042\u308b\u3002
\n\u307e\u3042\u3001\u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u4ee5\u524d\u306b\u3001\u3061\u3083\u3093\u3068\u52d5\u304b\u3057\u3066\u6c17\u4ed8\u304b\u306a\u3044\u79c1\u304c\u60aa\u3044\u3068\u3044\u3046\u8a71\u3067\u3042\u308b\u306e\u3060\u304c\u3002\u3002\u3002<\/p>\n
\u306a\u304a\u3001find_by\u30e1\u30bd\u30c3\u30c9\u3067\u306a\u304ffind\u30e1\u30bd\u30c3\u30c9\u306f\u3001\u4e3b\u30ad\u30fc\u306e\u307f\u3092\u6e21\u3057\u3066\u691c\u7d22\u3059\u308b\u3002\u30cf\u30c3\u30b7\u30e5\u306f\u53d7\u3051\u4ed8\u3051\u306a\u3044\u306e\u3067\u3001\u3053\u308c\u306f\u9593\u9055\u3048\u308b\u3053\u3068\u306f\u306a\u3044\u3060\u308d\u3046\u3002<\/p>\n
SomeModel.find(2)\n=> #<SomeModel id: 2, some_column: "fuga">\nSomeModel.find(id: 2)\n=> TypeError: can't cast Hash to integer......<\/code><\/pre>\nRails 4.2\u3067\u306ffind_by\u306e\u5b9f\u88c5\u306f\u3060\u3044\u3076\u5909\u308f\u3063\u3066\u3044\u308b\u3088\u3046\u3060\u304c\u3001\u3053\u306e\u4ef6\u306b\u95a2\u3057\u3066\u306f\u540c\u69d8\u306e\u3088\u3046\u3067\u3042\u308b\u3002<\/p>\n
\u3068\u3044\u3046\u308f\u3051\u3067\u3001\u305d\u3093\u306a\u3093\u9593\u9055\u3048\u306d\u3048\u3088\uff01\u3063\u3066\u3044\u3046\u58f0\u304c\u805e\u3053\u3048\u3066\u304d\u305d\u3046\u3067\u3059\u306d\u3002\u306a\u3093\u304b\u30d0\u30b0\u3092\u4f5c\u308a\u3053\u3093\u3060\u8a00\u3044\u8a33\u3092\u3057\u3066\u308b\u3088\u3046\u3067\u6050\u7e2e\u306a\u306e\u3067\u3059\u304c\u3001find_by\u306b\u6e21\u3059\u5f15\u6570\u306b\u306f\u3061\u3087\u3063\u3068\u6c17\u3092\u3064\u3051\u3088\u3046\u3068\u3044\u3046\u304a\u8a71\u3067\u3057\u305f\u3002<\/p>\n
\u30cd\u30b9\u30c8\u3057\u305f\u30e2\u30c7\u30eb\u306e\u5c5e\u6027\u66f4\u65b0\u6642\u306b\u30e6\u30cb\u30fc\u30af\u5236\u7d04\u3067\u30cf\u30de\u3063\u305f\u554f\u984c<\/h2>\n
ActiveRecord\u95a2\u9023\u3067\u3082\u3046\u4e00\u3064\u3061\u3087\u3063\u3068\u56f0\u3063\u305f\u30cd\u30bf\u3002<\/p>\n
\u4f8b\u3048\u3070\u3053\u3093\u306a\u30e2\u30c7\u30eb\u304c\u3042\u3063\u305f\u5834\u5408\u3002<\/p>\n
class Parent < ActiveRecord::Base\n has_many :children\n accepts_nested_attributes_for :children\nend\n\nclass Child < ActiveRecord::Base\n belongs_to :parent\n validates_uniqueness_of :name\nend<\/code><\/pre>\nParent\u30e2\u30c7\u30eb\u304b\u3089update_attributes\u3067\u8907\u6570\u306eChild\u30e2\u30c7\u30eb\u306ename\u3092\u4e00\u5ea6\u306b\u66f4\u65b0\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u304c\u3001\u300cvalidates_uniqueness_of :name\u300d\u3092\u66f8\u3044\u3066\u3042\u3063\u3066\u3082\u3001DB\u306b\u30e6\u30cb\u30fc\u30af\u5236\u7d04\u3092\u5165\u308c\u3066\u3044\u306a\u3044\u5834\u5408\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u4e00\u5ea6\u306b\u540c\u3058\u540d\u524d\u3092\u767b\u9332\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u3066\u3057\u307e\u3046\u3002<\/p>\n
?> p = Parent.create\n=> #<Parent id: 3, created_at: "2011-06-08 17:31:54", updated_at: "2011-06-08 17:31:54">\n>> p.update_attributes :children_attributes => [{:name => "Kid"}, {:name => "Kid"}]\n=> true\n>> Child.all.map(&:name)\n=> ["Kid", "Kid"]\n>> c = Child.first\n=> #<Child id: 4, parent_id: 3, name: "Kid", created_at: "2011-06-08 17:32:12", updated_at: "2011-06-08 17:32:12">\n>> c.save\n=> false\n>> c.errors.full_messages\n=> ["Name has already been taken"]<\/code><\/pre>\n\u3064\u307e\u308a\u3001'validates_uniqueness_of'\u3092\u3064\u3051\u3066\u3044\u3066\u3082children_attributes\u3067\u4e00\u5ea6\u306b\u540c\u3058\u5024\u306b\u66f4\u65b0\u3055\u308c\u305f\u5834\u5408\u306b\u306f\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\u306f\u52b9\u304b\u306a\u3044\u3002<\/p>\n
\u3053\u308c\u306faccepts_nested_attributes_for\u306b\u9650\u3063\u305f\u8a71\u3067\u306f\u306a\u304f\u3001validates_uniqueness_of\u4e00\u822c\u306b\u8a00\u3048\u308b\u8a71\u3067\u3042\u308b\u3002<\/p>\n
p = Parent.new\np.children << Child.new(:name => "Kid")\np.children << Child.new(:name => "Kid")\np.save\n=> true<\/code><\/pre>\n\u8abf\u3079\u3066\u307f\u308b\u3068\u3001\u540c\u3058\u3088\u3046\u306b\u56f0\u3063\u3066\u3044\u308b\u4eba\u304cRails\u306eissue\u3067\u305f\u304f\u3055\u3093\u898b\u3064\u304b\u3063\u305f\u3002
\nhttps:\/\/github.com\/rails\/rails\/issues\/1572<\/a> \uff08\u4e0a\u8a182\u3064\u306e\u30b5\u30f3\u30d7\u30eb\u30b3\u30fc\u30c9\u306f\u3001\u3053\u306eissue\u304b\u3089\u6d41\u7528\u3057\u305f\u3002\uff09
\nhttps:\/\/github.com\/rails\/rails\/issues\/4568<\/a><\/p>\n\u305d\u3057\u3066\u554f\u984c\u3092\u89e3\u6c7a\u3059\u308b\u3068\u3044\u3046PR\u3082\u3042\u308b\u306e\u3060\u304c\u3001\u6700\u7d42\u7684\u306b\u30de\u30fc\u30b8\u306f\u3055\u308c\u3066\u3044\u306a\u3044\u3002\u7d50\u5c40\u3001\u8907\u6570\u30e6\u30fc\u30b6\u304b\u3089\u306e\u66f4\u65b0\u306a\u3069\u3092\u8003\u3048\u308b\u3068\u3001DB\u5074\u306b\u30e6\u30cb\u30fc\u30af\u5236\u7d04\u3092\u5165\u308c\u308b\u5fc5\u8981\u304c\u3042\u308b\u3002\u3069\u3053\u307e\u3067Rails\u5074\u3067\u6551\u3046\u304b\u3068\u3044\u3046\u8a71\u3067\u3001\u4eca\u56de\u306e\u5834\u5408\u3001\u8907\u96d1\u306a\u30b3\u30fc\u30c9\u3092\u5165\u308c\u8fbc\u3080\u5272\u306b\u306f\u3001\u6839\u672c\u7684\u306a\u89e3\u6c7a\u306b\u306f\u306a\u3089\u306a\u3044\u305f\u3081\u3001Rails\u5074\u306b\u306f\u5165\u308c\u305f\u304f\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u306e\u3088\u3046\u3067\u3042\u308b\u3002<\/p>\n
\u305d\u308c\u306f\u3082\u3063\u3068\u3082\u306a\u8a71\u3060\u3068\u601d\u3046\u306e\u3060\u3051\u308c\u3069\u3082\u3001\u8907\u6570\u30e6\u30fc\u30b6\u304b\u3089\u306e\u540c\u6642\u66f4\u65b0\u304c\u4ed5\u69d8\u7684\u306b\u901a\u5e38\u306f\u8d70\u3089\u306a\u3044\u3088\u3046\u306a\u5834\u5408\u3001\u57fa\u672c\u7684\u306b\u306fRails\u5074\u3067\u30e6\u30cb\u30fc\u30af\u6027\u3092\u4fdd\u8a3c\u3057\u3064\u3064\u3001\u4e07\u304c\u4e00\u306e\u5834\u5408\u306b\u3060\u3051DB\u306e\u30e6\u30cb\u30fc\u30af\u5236\u7d04\u306b\u5f15\u3063\u304b\u304b\u308b\u3053\u3068\u306b\u3088\u308bInternal Server Error\u3067\u3044\u3044\u3084\u3068\u3044\u3046\u30cb\u30fc\u30ba\u306f\u3051\u3063\u3053\u3046\u3042\u308b\u306e\u3067\u306f\u3068\u601d\u3046\u3002\u3061\u3087\u3063\u3068\u30b5\u30dc\u308a\u3059\u304e\u304b\u306a\u3002\u4f55\u304b\u52d8\u9055\u3044\u306a\u3069\u3057\u3066\u3044\u305f\u3089\u3054\u3081\u3093\u306a\u3055\u3044\u3002<\/p>\n