Ruby on rails 要添加字段的第一个课程表打开，键入Boolean；rake db:迁移操作错误？

！！！！！然后操作

class AddOpenAttributeToCourses < ActiveRecord::Migration
  def change
    add_column :courses, :open, :boolean
    change_column_default(:courses, :open, {:from=>true, :to=>false})
  end
end

---

您可以创建列并在一行中设置默认值：

rake db:migrate
== 20161126133112 AddOpenAttributeToCourses: migrating ========================
-- add_column(:courses, :open, :boolean)
   -> 0.1047s
-- change_column_default(:courses, :open, {:from=>true, :to=>false})
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:

PG::InvalidTextRepresentation: ERROR:  invalid input syntax for type boolean: "---
:from: true
:to: false
"
: ALTER TABLE "courses" ALTER COLUMN "open" SET DEFAULT '---
:from: true
:to: false
'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `async_exec'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `block in execute'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/abstract_adapter.rb:472:in `block in log'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5.2/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/abstract_adapter.rb:466:in `log'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:154:in `execute'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/postgresql/schema_statements.rb:455:in `change_column_default'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:665:in `block in method_missing'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:634:in `block in say_with_time'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:634:in `say_with_time'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:654:in `method_missing'
/home/ubuntu/workspace/db/migrate/20161126133112_add_open_attribute_to_courses.rb:4:in `change'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:608:in `exec_migration'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:592:in `block (2 levels) in migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:591:in `block in migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/abstract/connection_pool.rb:292:in `with_connection'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:590:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:768:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:998:in `block in execute_migration_in_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:1044:in `block in ddl_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `block in transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/abstract/transaction.rb:184:in `within_new_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/transactions.rb:220:in `transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:1044:in `ddl_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:997:in `execute_migration_in_transaction'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:959:in `block in migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:955:in `each'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:955:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:823:in `up'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/migration.rb:801:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/tasks/database_tasks.rb:137:in `migrate'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.5.2/lib/active_record/railties/databases.rake:44:in `block (2 levels) in <top (required)>'
/usr/local/rvm/gems/ruby-2.3.0/gems/rake-11.2.2/exe/rake:27:in `<top (required)>'
ActiveRecord::StatementInvalid: PG::InvalidTextRepresentation: ERROR:  invalid input syntax for type boolean: "---
:from: true
:to: false
"

不知道你为什么会犯这样的错误。也许是因为你说把默认值从false改为true，但是默认值不是false，实际上是nil

您正在尝试使用：

更改\列\默认表\名称、列\名称、默认值\或\更改 [...] 传递包含：from和：to的散列将使此更改在迁移中可逆：

add_column :courses, :open, :boolean, default: true

与：

更改\u列\u默认表\u名称、列\u名称、默认值 为列[…]设置新的默认值

您在SQL中看到的有趣的东西：

change_column_default(:posts, :state, from: nil, to: "draft")

是{:from=>true，：to=>false}Ruby哈希BTW的YAML版本

您需要使用单独的向上和向下方法以及更简单版本的change\u column\u default与Rails4：

---
:from: true
:to: false

或者在创建列时只设置默认值：

def up
  change_column_default(:courses, :open, false)
end
def down
  change_column_default(:courses, :open, true)
end

---

顺便说一句，由于您在添加列时未指定：default，因此默认值为null，而不是true。

请编辑您的问题，准确告诉我们您打算做什么，以及预期的结果是什么？发布一个类和一条错误消息并不能很好地描述您的问题。

class AddOpenAttributeToCourses < ActiveRecord::Migration
  def change
    add_column :courses, :open, :boolean, :default => false
  end
end