命令 bin/rails db:migrate 抛出错误，如下所示：
---
rails aborted!
ArgumentError: wrong number of arguments (given 4, expected 1)
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:1062:in `type_to_sql'
/var/lib/gems/2.3.0/gems/activerecord-mysql2-adapter-0.0.3/lib/active_record/connection_adapters/mysql2_adapter.rb:520:in `type_to_sql'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_creation.rb:17:in `type_to_sql'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_creation.rb:32:in `visit_ColumnDefinition'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_creation.rb:14:in `accept'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_creation.rb:45:in `block in visit_TableDefinition'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_creation.rb:45:in `map'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_creation.rb:45:in `visit_TableDefinition'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_creation.rb:14:in `accept'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:288:in `create_table'
/var/lib/gems/2.3.0/gems/activerecord-mysql2-adapter-0.0.3/lib/active_record/connection_adapters/mysql2_adapter.rb:439:in `create_table'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/schema_migration.rb:27:in `create_table'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/migration.rb:1125:in `initialize'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/migration.rb:1007:in `new'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/migration.rb:1007:in `up'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/migration.rb:985:in `migrate'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/tasks/database_tasks.rb:171:in `migrate'
/var/lib/gems/2.3.0/gems/activerecord-5.1.1/lib/active_record/railties/databases.rake:58:in `block (2 levels) in <top (required)>'
/var/lib/gems/2.3.0/gems/railties-5.1.1/lib/rails/commands/rake/rake_command.rb:21:in `block in perform'
/var/lib/gems/2.3.0/gems/railties-5.1.1/lib/rails/commands/rake/rake_command.rb:18:in `perform'
/var/lib/gems/2.3.0/gems/railties-5.1.1/lib/rails/command.rb:46:in `invoke'
/var/lib/gems/2.3.0/gems/railties-5.1.1/lib/rails/commands.rb:16:in `<top (required)>'
/home/binu/workspace/ruby/demo/bin/rails:9:in `require'
/home/binu/workspace/ruby/demo/bin/rails:9:in `<top (required)>'
/var/lib/gems/2.3.0/gems/spring-2.0.1/lib/spring/client/rails.rb:28:in `load'
/var/lib/gems/2.3.0/gems/spring-2.0.1/lib/spring/client/rails.rb:28:in `call'
/var/lib/gems/2.3.0/gems/spring-2.0.1/lib/spring/client/command.rb:7:in …如何在保持其长度为at的同时确保此数组的唯一性5？
def fixed
5.times.collect { SecureRandom.random_number(10) }
end
这种行为似乎很奇怪：
5.times.collect.uniq { SecureRandom.random_number(10) }
# => [0, 2, 3, 4]
5.times.collect.uniq { SecureRandom.random_number(10) }
# => [0, 1, 3]
5.times.collect.uniq { SecureRandom.random_number(10) }
# => [0, 1, 2, 3, 4]
5.times.collect.uniq { SecureRandom.random_number(10) }
# => [0, 1, 2, 4]
5.times.collect.uniq { SecureRandom.random_number(10) }
# => [0, 1, 2, 3]
我的输入哈希:
h = [
{user_id: 1, bookings_nd: 3},
{user_id: 2, bookings_nd: 10},
{user_id: 3, bookings_nd: 2}
]
我需要:
h = [
{user_id: 2, bookings_nd: 10},
{user_id: 1, bookings_nd: 3},
{user_id: 3, bookings_nd: 2}
]
怎么做？
我正在使用 Clear bit gem。如何在 Rails 应用程序中调用外部 API 并在没有默认数据库的情况下发送数据来存储数据。我需要构建一个像 Clear bit 表单这样的表单并来回发送数据。我需要控制器和模型吗？相同？
今天我得到了一个给定数组和'target'的任务,它是该列表中2个整数的总和.一段时间后,我出来了草案解决方案,但它似乎没有通过所有的测试.算法似乎在[0]两次考虑整数.
def two_sum(numbers, target)
numbers.combination 2 do |a, b|
if a + b == target
return numbers.index(a), numbers.index(b)
end
end
end
print two_sum([1, 2, 3], 4) # Expected [0, 2] *OK
print two_sum([1234, 5678, 9012], 14690) # Expected [1, 2] *OK
print two_sum([2, 2, 3], 4) # Expected [0, 1]) but I get [0, 0]
我试图首先使用.map而不是.combination(2)方法,但结果完全相同: - /
我正在构建一个Rails 5应用程序。在这个应用程序中，我得到了一个用户模型和一个订阅模型。我希望能够获得所有拥有有效订阅的用户。
用户
has_one：订阅
- id,
- name
- email
订阅
当属：用户
- id
- user_id
- title
- active (boolean)
我需要能够进行如下查询（如下）。换句话说，我需要找到所有不仅获得订阅而且还将active属性设置为true的用户。
User.with_active_subscriptions
我想我可能需要做一个示波器，但不知道如何做。