Question

当我使用t.string或t.number时，我无法创建数据库列。

当我做rake db：migrate时我得到了这个

C:\Ruby\joker\chapter3>rake db:migrate
(in C:/Ruby/joker/chapter3)
==  CreateComicBooks: migrating ===============================================
-- create_table(:comic_books)
   -> 0.0630s
==  CreateComicBooks: migrated (0.0640s) ======================================

我使用了以下代码

class ComicBook < ActiveRecord::Base
def self.up
create_table :comic_books do |t|
t.string :title
t.string :writer
t.string :artist
t.integer :issue
t.string :publisher
t.timestamps
end
end

def self.down
    drop_table :comic_books
    end
end

我也试过

class ComicBook < ActiveRecord::Base
def self.up
create_table :comic_books do |t|
t.column "title", :string
t.column "writer", :string
t.column "artist", :string
t.column "issue", :number
t.column "publisher", :string
t.timestamps
end
end

def self.down
# called when a migration is reversed
    drop_table :comic_books
    end
end

在数据库中我得到以下输出

mysql> show tables;
+-----------------------------------+
| Tables_in_comic_books_development |
+-----------------------------------+
| comic_books                       |
| schema_migrations                 |
+-----------------------------------+
2 rows in set (0.00 sec)

mysql> describe comic_books;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| created_at | datetime | YES  |     | NULL    |                |
| updated_at | datetime | YES  |     | NULL    |                |
+------------+----------+------+-----+---------+----------------+
3 rows in set (0.01 sec)

mysql>

现在，当我尝试创建新记录时，我正在接受此

C:\Ruby\joker\chapter3>ruby script/console
Loading development environment (Rails 2.3.8)
>> mycb = ComicBook.new
=> #<ComicBook id: nil, created_at: nil, updated_at: nil>
>> mycb.title = 'All new'
NoMethodError: undefined method `title=' for #<ComicBook id: nil, created_at: ni
l, updated_at: nil>
        from C:/Ruby/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record
/attribute_methods.rb:259:in `method_missing'
        from (irb):2

我认为这是一个非常小的错误，但我无法弄明白。

期待您的帮助和支持。

谢谢

Answer 1

迁移顶部的这条线是什么？这只是你问题中的错误吗？

ComicBook < ActiveRecord::Base

看起来您将代码放在模型中而不是迁移中！？

在/ db / migrate文件夹中查找顶部应该有类似内容的文件

class CreateComicBooks < ActiveRecord::Migration

看起来你已经使用了一个生成器来创建迁移（这很好），然后运行rake db：migrate，这将解释为什么你在数据库中只有id和timestamps的表。您可能希望运行rake db：rollback，然后将您的字段添加到迁移中的def self.up部分并重新迁移。

Rails中的简单数据库迁移错误

1 个答案: