Grails标准预测 - 获取行数 [英] Grails criteria projections - get rows count

问题描述

我有Hotel实体：

  class Hotel {
 City city 
} 
  

现在，我需要计算给定城市的酒店数量。
可以这样做：

  def hotels = Hotel.findAllByCity（city）
 def cnt = hotels.size（）
  

但它非常脏。它似乎与标准，它会更好，但我不知道如何实现它...

解决方案

有动态计数器以及域对象上的查找器：

  Hotel.countByCity（city）
  

更多详情请参阅用户指南，当然

I have Hotel entity:

class Hotel {
City city
}

Now, i need count of hotels with given city. It could be done in this way:

def hotels = Hotel.findAllByCity(city)
def cnt = hotels.size()

But it's very dirty way. It seems that with criteria it would be better, but i have no idea how to implement it...

解决方案

There are dynamic counters as well as finders on domain objects:

Hotel.countByCity(city)

More details in the user guide, of course

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