ActiveRecord的使用拒绝方法

问题描述

我有一个模型，从获取特定城市的所有游戏。当我拿到这些游戏我要过滤他们，我想使用拒绝的方法，但我遇到了一个错误，我想明白了。

I have a model that fetches all the games from a particular city. When I get those games I want to filter them and I would like to use the reject method, but I'm running into an error I'm trying to understand.

# STEP 1 - Model
class Matches < ActiveRecord::Base
  def self.total_losses(cities)
    reject{ |a| cities.include?(a.winner) }.count
  end
end

# STEP 2 - Controller
@games = Matches.find_matches_by("Toronto")
# GOOD! - Returns ActiveRecord::Relation

# STEP 3 - View
cities = ["Toronto", "NYC"]
@games.total_losses(cities)
# FAIL - undefined method reject for #<Class:0x00000101ee6360>

# STEP 3 - View
cities = ["Toronto", "NYC"]
@games.reject{ |a| cities.include?(a.winner) }.count
# PASSES - it returns a number.

为什么拒绝在我看来不能在我的模型，但不是？

Why does reject fail in my model but not in my view ?

推荐答案

所不同的是，你在呼唤拒绝的对象。在视图中， @games 的活动记录对象的数组，因此调用 @ games.reject 使用阵列＃拒绝。在你的模型，你调用拒绝在自中的一类方法，这意味着它试图调用 Matches.reject ，它不存在。您需要首先获取的记录，像这样的：

The difference is the object you are calling reject on. In the view, @games is an array of Active Record objects, so calling @games.reject uses Array#reject. In your model, you're calling reject on self in a class method, meaning it's attempting to call Matches.reject, which doesn't exist. You need to fetch records first, like this:

def self.total_losses(cities)
  all.reject { |a| cities.include(a.winner) }.count
end

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