Phoenix username 已被人占用

如果你已完成上一章，你可能已經(jīng)猜到，這章的規(guī)則要怎么寫，不過在那之前，還是讓我們先寫個測試：

diff --git a/test/tv_recipe/users_test.exs b/test/tv_recipe/users_test.exs
index 4c174ab..47df0c7 100644
--- a/test/tv_recipe/users_test.exs
+++ b/test/tv_recipe/users_test.exs
@@ -20,4 +20,13 @@ defmodule TvRecipe.UserTest do
     attrs = %{@valid_attrs | username: ""}
     assert %{username: ["請?zhí)顚?]} = errors_on(%User{}, attrs)
   end
+
+  test "username should be unique" do
+    # 在測試數(shù)據(jù)庫中插入新用戶
+    user_changeset = User.changeset(%User{}, @valid_attrs)
+    TvRecipe.Repo.insert! user_changeset
+
+    # 嘗試插入同名用戶，應報告錯誤
+    assert {:error, changeset} = TvRecipe.Repo.insert(User.changeset(%User{}, %{@valid_attrs | email: "chenxsan+1@gmail.com"}))
+  end
 end

此時運行 mix test test/tv_recipe/users_test.exs，我們的測試會全部通過。這是因為，我們在執(zhí)行 mix phx.gen.html 命令時，指定了 unique 給 username 字段，這樣生成的 User 結構里，我們已經(jīng)有了唯一性的限定規(guī)則，如下所示：

def changeset(struct, params \\ %{}) do
  struct
  |> cast(params, [:username, :email, :password])
  |> validate_required([:username, :email, :password], message: "請?zhí)顚?)
  |> unique_constraint(:username)
  |> unique_constraint(:email)
end

但上面的測試里，我們只知道插入同名用戶時，Phoenix 會返回錯誤，至于錯誤是什么，我們還沒有檢查。

我們來完善下我們上面的測試代碼：

diff --git a/test/tv_recipe/users_test.exs b/test/tv_recipe/users_test.exs
index 47df0c7..9748671 100644
--- a/test/tv_recipe/users_test.exs
+++ b/test/tv_recipe/users_test.exs
@@ -28,5 +28,8 @@ defmodule TvRecipe.UserTest do

     # 嘗試插入同名用戶，應報告錯誤
     assert {:error, changeset} = TvRecipe.Repo.insert(user_changeset)
+
+    # 錯誤信息為“用戶名已被人占用”
+    assert %{username: ["用戶名已被人占用"]} = errors_on(changeset)
   end
 end

再次運行 mix test test/tv_recipe/users_test.exs 的結果是：

$ mix test test/tv_recipe/users_test.exs
.

  1) test username should be unique (TvRecipe.UserTest)
     test/tv_recipe/users_test.exs:24
     Assertion with in failed
     code:  %{username: ["用戶名已被人占用"]} = errors_on(changeset)
     left:  %{username: ["用戶名已被人占用"]}
     right: [username: "has already been taken"]
     stacktrace:
       test/tv_recipe/users_test.exs:33: (test)

..

Finished in 0.1 seconds
4 tests, 1 failure

測試不通過。因為"用戶名已被人占用"不等于 "has already been taken"。

這是當然，我們還未自定義用戶名重復時的提示消息。

打開 lib/tv_recipe/users/user.ex 文件，做如下修改：

diff --git a/lib/tv_recipe/users/user.ex b/lib/tv_recipe/users/user.ex
index 87ce321..88ad2af 100644
--- a/lib/tv_recipe/users/user.ex
+++ b/lib/tv_recipe/users/user.ex
@@ -16,7 +16,7 @@ defmodule TvRecipe.User do
     struct
     |> cast(params, [:username, :email, :password])
     |> validate_required([:username, :email, :password], message: "請?zhí)顚?)
-    |> unique_constraint(:username)
+    |> unique_constraint(:username, message: "用戶名已被人占用")
     |> unique_constraint(:email)
   end
 end

再跑一次測試，順利通過。

結束這一章了？不不不，還有一點，我們或許遺漏了，就是用戶名的大小寫。

大小寫敏感

我們先寫個測試驗證一下：

diff --git a/test/tv_recipe/users_test.exs b/test/tv_recipe/users_test.exs
index 9748671..44cb21b 100644
--- a/test/tv_recipe/users_test.exs
+++ b/test/tv_recipe/users_test.exs
@@ -32,4 +32,13 @@ defmodule TvRecipe.UserTest do
     # 錯誤信息為“用戶名已被人占用”
     assert %{username: ["用戶名已被人占用"]} = errors_on(changeset)
   end
+
+  test "username should be case insensitive" do
+    user_changeset = User.changeset(%User{}, @valid_attrs)
+    TvRecipe.Repo.insert! user_changeset
+
+    # 嘗試插入大小寫不一致的用戶名，應報告錯誤
+    another_user_changeset = User.changeset(%User{}, %{@valid_attrs | username: "Chenxsan", email: "chenxsan+1@gmail.com"})
+    assert {:error, changeset} = TvRecipe.Repo.insert(another_user_changeset)
+  end
 end

運行測試的結果是：

$ mix test test/tv_recipe/users_test.exs
warning: variable "changeset" is unused
  test/tv_recipe/users_test.exs:42

...

  1) test username should be case insensitive (TvRecipe.UserTest)
     test/tv_recipe/users_test.exs:36
     match (=) failed
     code:  {:error, changeset} = TvRecipe.Repo.insert(another_user_changeset)
     right: {:ok,
             %TvRecipe.User{__meta__: #Ecto.Schema.Metadata<:loaded, "users">,
              email: "chenxsan+1@gmail.com", id: 36,
              inserted_at: ~N[2017-01-24 11:57:43.741097],
              password: "some content",
              updated_at: ~N[2017-01-24 11:57:43.741109], username: "Chenxsan"}}
     stacktrace:
       test/tv_recipe/users_test.exs:42: (test)

.

Finished in 0.1 seconds
5 tests, 1 failure

我們的判斷錯了。無論是 chenxsan 還是 Chenxsan 的用戶名，我們都插入成功，這當然不是我們期望的結果。

我們來看看 unique_constraint 文檔的一段說明：

Unfortunately, different databases provide different guarantees when it comes to case-sensitiveness. For example, in MySQL, comparisons are case-insensitive by default. In Postgres, users can define case insensitive column by using the :citext type/extension.

不同數(shù)據(jù)庫對大小寫的處理不一樣，比如 MySQL 是大小寫不敏感的，而默認情況下，PostgreSQL 字段是大小寫敏感的，不過我們可以使用 citext 擴展類型。

如果不用 citext，文檔中仍有其它辦法：

If for some reason your database does not support case insensitive columns, you can explicitly downcase values before inserting/updating them

根據(jù)提示，我們的 user.ex 代碼可以做如下修改：

diff --git a/lib/tv_recipe/users/user.ex b/lib/tv_recipe/users/user.ex
index 88ad2af..fc07824 100644
--- a/lib/tv_recipe/users/user.ex
+++ b/lib/tv_recipe/users/user.ex
@@ -16,6 +16,7 @@ defmodule TvRecipe.User do
     struct
     |> cast(params, [:username, :email, :password])
     |> validate_required([:username, :email, :password], message: "請?zhí)顚?)
+    |> update_change(:username, &String.downcase/1)
     |> unique_constraint(:username, message: "用戶名已被人占用")
     |> unique_constraint(:email)
   end

再跑一次測試，測試通過。

可是，如果我一定要用 CHenxsan 這個用戶名呢？String.downcase 的處理方式，導致我們只能使用小寫的 chenxsan。

我們還有個辦法，只是比較復雜。

數(shù)據(jù)庫遷移

在用戶注冊一章，我們用 mix phx.gen.html 生成了許多樣板文件，其中有一條：

* creating priv/repo/migrations/20170123145857_create_user.exs

打開該文件，它的內(nèi)容如下：

defmodule TvRecipe.Repo.Migrations.CreateUser do
  use Ecto.Migration

  def change do
    create table(:users) do
      add :username, :string
      add :email, :string
      add :password, :string

      timestamps()
    end
    create unique_index(:users, [:username])
    create unique_index(:users, [:email])

  end
end

正是 create unique_index(:users, [:username]) 一行，在數(shù)據(jù)庫中限定了 username 的唯一性。

只是它沒有處理大小寫的問題。但我們能夠處理處理，只要把它改成如下：

create unique_index(:users, ["lower(username)"])

那么要怎樣去掉舊的 unique_index 而換上新的呢？

Ecto 提供了一個 mix ecto.gen.migration 功能用于這類轉換。

在命令行下創(chuàng)建一個試試：

$ cd tv_recipe
$ mix ecto.gen.migration alter_user_username_index
* creating priv/repo/migrations
* creating priv/repo/migrations/20170124123616_alter_user_username_index.exs

打開新創(chuàng)建的 20170124123616_alter_user_username_index.exs 文件，做如下修改：

diff --git a/priv/repo/migrations/20170124123616_alter_user_username_index.exs b/priv/repo/migrations/20170124123616_alter_user_username_index.exs
index 5723a10..4060abf 100644
--- a/priv/repo/migrations/20170124123616_alter_user_username_index.exs
+++ b/priv/repo/migrations/20170124123616_alter_user_username_index.exs
@@ -2,6 +2,7 @@ defmodule TvRecipe.Repo.Migrations.AlterUserUsernameIndex do
   use Ecto.Migration

   def change do
+    drop index(:users, [:username]) # 移除舊索引
+    create unique_index(:users, ["lower(username)"]) # 增加新索引
   end
 end

然后在命令行中執(zhí)行 mix ecto.migrate，把遷移文件的修改落實到數(shù)據(jù)庫中：

$ mix ecto.migrate

20:39:44.900 [info]  == Running TvRecipe.Repo.Migrations.AlterUserUsernameIndex.change/0 forward

20:39:44.900 [info]  drop index users_username_index

20:39:44.930 [info]  create index users_lower_username_index

20:39:44.940 [info]  == Migrated in 0.0s

最后要記得將此前 user.ex 文件中 String.downcase 的修改撤銷掉：

diff --git a/lib/tv_recipe/users/user.ex b/lib/tv_recipe/users/user.ex
index fc07824..88ad2af 100644
--- a/lib/tv_recipe/users/user.ex
+++ b/lib/tv_recipe/users/user.ex
@@ -16,7 +16,6 @@ defmodule TvRecipe.User do
     struct
     |> cast(params, [:username, :email, :password])
     |> validate_required([:username, :email, :password], message: "請?zhí)顚?)
-    |> update_change(:username, &String.downcase/1)
     |> unique_constraint(:username, message: "用戶名已被人占用")
     |> unique_constraint(:email)
   end

再運行測試看看：

mix test test/tv_recipe/users_test.exs
warning: variable "changeset" is unused
  test/tv_recipe/users_test.exs:42

.

  1) test username should be case insensitive (TvRecipe.UserTest)
     test/tv_recipe/users_test.exs:36
     ** (Ecto.ConstraintError) constraint error when attempting to insert struct:

         * unique: users_lower_username_index

     If you would like to convert this constraint into an error, please
     call unique_constraint/3 in your changeset and define the proper
     constraint name. The changeset defined the following constraints:

         * unique: users_email_index
         * unique: users_username_index

     stacktrace:
       (ecto) lib/ecto/repo/schema.ex:493: anonymous fn/4 in Ecto.Repo.Schema.constraints_to_errors/3
       (elixir) lib/enum.ex:1229: Enum."-map/2-lists^map/1-0-"/2
       (ecto) lib/ecto/repo/schema.ex:479: Ecto.Repo.Schema.constraints_to_errors/3
       (ecto) lib/ecto/repo/schema.ex:213: anonymous fn/13 in Ecto.Repo.Schema.do_insert/4
       test/tv_recipe/users_test.exs:42: (test)

.

  2) test username should be unique (TvRecipe.UserTest)
     test/tv_recipe/users_test.exs:24
     ** (Ecto.ConstraintError) constraint error when attempting to insert struct:

         * unique: users_lower_username_index

     If you would like to convert this constraint into an error, please
     call unique_constraint/3 in your changeset and define the proper
     constraint name. The changeset defined the following constraints:

         * unique: users_email_index
         * unique: users_username_index

     stacktrace:
       (ecto) lib/ecto/repo/schema.ex:493: anonymous fn/4 in Ecto.Repo.Schema.constraints_to_errors/3
       (elixir) lib/enum.ex:1229: Enum."-map/2-lists^map/1-0-"/2
       (ecto) lib/ecto/repo/schema.ex:479: Ecto.Repo.Schema.constraints_to_errors/3
       (ecto) lib/ecto/repo/schema.ex:213: anonymous fn/13 in Ecto.Repo.Schema.do_insert/4
       test/tv_recipe/users_test.exs:30: (test)

.

Finished in 0.1 seconds
5 tests, 2 failures

情況變得更糟糕了，報告了 2 個錯誤。這是因為索引名稱已經(jīng)改變，而我們的代碼還在使用默認的舊索引名。我們需要在 unique_constraint 里明確指出索引名稱：

diff --git a/lib/tv_recipe/users/user.ex b/lib/tv_recipe/users/user.ex
index 88ad2af..08e4054 100644
--- a/lib/tv_recipe/users/user.ex
+++ b/lib/tv_recipe/users/user.ex
@@ -16,7 +16,7 @@ defmodule TvRecipe.User do
     struct
     |> cast(params, [:username, :email, :password])
     |> validate_required([:username, :email, :password], message: "請?zhí)顚?)
-    |> unique_constraint(:username, message: "用戶名已被人占用")
+    |> unique_constraint(:username, name: :users_lower_username_index, message: "用戶名已被人占用")
     |> unique_constraint(:email)
   end
 end

再跑一遍測試：

$ mix test test/tv_recipe/users_test.exs
warning: variable "changeset" is unused
  test/tv_recipe/users_test.exs:42

.....

Finished in 0.1 seconds
5 tests, 0 failures

悉數(shù)通過。

但眼尖的你可能已經(jīng)注意到，我們的測試報告里有一條：

warning: variable "changeset" is unused

在 Elixir 下，如果有定義的變量未曾使用到，編譯時就會出現(xiàn)警告。

上面這條警告對應的是測試代碼中的這一行：

assert {:error, changeset} = TvRecipe.Repo.insert(another_user_changeset)

我們只斷定了插入數(shù)據(jù)庫失敗，還沒有檢查 changeset 里的錯誤。

讓我們完善下測試：

diff --git a/test/tv_recipe/users_test.exs b/test/tv_recipe/users_test.exs
index 9451c2d..975c7b1 100644
--- a/test/tv_recipe/users_test.exs
+++ b/test/tv_recipe/users_test.exs
@@ -40,5 +40,6 @@ defmodule TvRecipe.UserTest do
     # 嘗試插入大小寫不一致的用戶名，應報告錯誤
     another_user_changeset = User.changeset(%User{}, %{@valid_attrs | username: "Chenxsan", email: "chenxsan+1@gmail.com"})
     assert {:error, changeset} = TvRecipe.Repo.insert(another_user_changeset)
+    assert %{username: ["用戶名已被人占用"]} = errors_on(changeset)
   end
 end

再次運行測試，悉數(shù)通過。