定义关系Ruby-on-Rails

如何解决定义关系Ruby-on-Rails

我有一个“位置”表和一个“角色”表，

位置表：

id|location_name|location_code|category|
1 |  location1  |   0001      | Urban  |
2 |  location2  |   0002      | Rural  |
3 |  location3  |   0003      |Suburban|
________________________________________

收入表：

id|role_code|rural|urban|suburban|
1 |   1001  |  5  |  10 |   15   |
2 |   1002  |  7  |  12 |   17   |
1 |   1003  |  9  |  14 |   19   |
__________________________________

位置表用于了解区域（农村，城市或郊区）的类别，角色表用于根据位置类别来了解收入的价格。

我如何将两个表连接在一起，以便每当用户放置位置和角色时，他们都能看到价格？

解决方法

当前结构本质上不是非常可扩展的。我强烈建议您更改数据的结构方式。看下面的例子。

# Instead of storing the location category in as text you can store references
#   of location_category in locations & revenues table
class LocationType # Location Category
end
# +----+-----------+
# | id | name      |
# +----+-----------+
# |  1 | Urban     |
# +----+-----------+
# |  2 | Rural     |
# +----+-----------+
# |  3 | Sub Urban |
# +----+-----------+


# Similarly instead of storing role_code,you can store references to roles 
#   in your revenue table
class Role
end
# +----+------+--------+
# | id | code | name   |
# +----+------+--------+
# |  1 | 1001 | Role 1 |
# +----+------+--------+
# |  2 | 1002 | Role 2 |
# +----+------+--------+
# |  3 | 1003 | Role 3 |
# +----+------+--------+

class Location
  belongs_to :location_type
end
# +----+-----------+---------+------------------+
# | id | name      | code    | location_type_id |
# +----+-----------+---------+------------------+
# |  1 | location1 | 001     |                1 |
# +----+-----------+---------+------------------+
# |  2 | location2 | 002     |                2 |
# +----+-----------+---------+------------------+
# |  3 | location3 | 003     |                3 |
# +----+-----------+---------+------------------+

class Revenue
  belongs_to :location_type
  belongs_to :role
end
# References for roles & location_type stored instead of actual values
# +----+-----------+---------+------------------+
# | id | role_id   | revenue | location_type_id |
# +----+-----------+---------+------------------+
# |  1 |         1 |       5 |                2 |
# +----+-----------+---------+------------------+
# |  2 |         2 |       7 |                2 |
# +----+-----------+---------+------------------+
# |  3 |         3 |       9 |                2 |
# +----+-----------+---------+------------------+
# |  4 |         1 |      10 |                1 |
# +----+-----------+---------+------------------+
# |  5 |         2 |      12 |                1 |
# +----+-----------+---------+------------------+
# |  6 |         3 |      14 |                1 |
# +----+-----------+---------+------------------+
# |  7 |         1 |      15 |                3 |
# +----+-----------+---------+------------------+
# |  8 |         2 |      17 |                3 |
# +----+-----------+---------+------------------+
# |  9 |         3 |      19 |                3 |
# +----+-----------+---------+------------------+

现在，通过这种结构，您可以在数据库上运行最优查询以提取数据。

# Example
location_type_id = params[:location_type_id]
role_id = params[:role_id]

@revenue = Revenue.where({
  location_type_id: location_type_id,role_id: role_id
}).sum(:revenue)

如果您还希望在“收入”表中添加location_id，则可以找到特定位置的收入，如下所示：

@revenue = Revenue.where({
  role_id: role_id,location_id: location_id
}).sum(:revenue)

,

如果用户放置location2和角色1003，则可以执行以下操作：

location = params[:location] # or some other way to get the input
role = params[:role] # or some other way to get the input

location_category = Location.find_by(name: location).category.downcase
# now location_category will be rural

Reveneu.find_by(role_code: role).send(location_category)
# with the .send method you can access the column that you need(in this case rural)

,

假设用户在用户模型中具有角色代码和位置名称-

user = User.first
category = Location.find_by(name: location).category.downcase
price = Revenue.find_by(role_code: user.role_code).send(category)
puts "Your price is #{price}"

,

获取价格的一种简单方法是使一个函数接受一个Location对象（user_entered_location）和一个Revenue对象（user_entered_revenue）并返回一个价格。

def get_price(user_entered_location,user_entered_revenue)
    if user_entered_location.category=="Urban"
        return user_entered_revenue.urban
    elsif user_entered_location.category=="Suburban"
        return user_entered_revenue.suburban
    else
        return user_entered_revenue.rural
end

您还可以查看JSONPlaceholder

,

最简单的方法是使用if语句来检查位置是城市，乡村还是郊区。

我假设您想在其他模型中使用价格，因此我在下面的代码示例中将模型称为transaction。

if transaction_params[:price].blank?
    
  if @transaction.location.category == 'Rural'
    @transaction.price = @transaction.revenue.rural
  elsif @transaction.location.category == 'Suburban'
    @transaction.price = @transaction.revenue.suburban
  else
    @transaction.price = @transaction.revenue.urban
  end
end

您可以通过事务控制器中的create方法执行此操作。