Ruby-on-rails 通过子对象的最大字段值查找 ActiveRecord 对象？
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Find ActiveRecord object by maximum field value of a child object?
提问by justinxreese
How can I find the object associated with the results of an ActiveRecord Calculation rather than a value?
如何找到与 ActiveRecord 计算的结果而不是值相关联的对象？
For example I have @parent which has many children. I would like to find the child with the maximum 'value'.
例如我有@parent，它有很多孩子。我想找到具有最大“价值”的孩子。
I understand that I can do @parent.children.maximum(:value), but this returns the maximum value. Is there a method similar to maximum and minimum that returns the entire object instead of the value so that I can use different fields from the maximum object?
我知道我可以做@parent.children.maximum(:value)，但这会返回最大值。是否有类似于最大值和最小值的方法返回整个对象而不是值，以便我可以使用来自最大值对象的不同字段？
回答by fl00r
@parent.children.order("value DESC").first
回答by Will Ayd
Not sure if this is the most efficient but once you have the maximum value you can pass that along in a hash to get the object
不确定这是否是最有效的，但是一旦您拥有最大值，您就可以将其以散列形式传递以获取对象
@maxvalue = @parent.children.maximum(:value)
@myObject = @parent.children.where(:value => @maxvalue)
回答by SirLenz0rlot
回答by jemminger
@parent.children.first(:conditions => {:value => @parent.children.maximum(:value)})
