ActiveRecord 和使用拒绝方法
我有一个模型可以获取特定城市的所有游戏。当我得到这些游戏时，我想过滤它们，并且想使用 reject 方法，但我遇到了一个我试图理解的错误。
# 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 reject 在我的模型中失败，但在我的视图中却没有？
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.
Why does reject fail in my model but not in my view ?
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区别在于您调用
reject的对象。在视图中，@games是 Active Record 对象的数组，因此调用@games.reject使用Array#reject。在您的模型中，您在类方法中对self调用reject，这意味着它正在尝试调用Matches.reject，而这不会存在。您需要首先获取记录，如下所示：The difference is the object you are calling
rejecton. In the view,@gamesis an array of Active Record objects, so calling@games.rejectusesArray#reject. In your model, you're callingrejectonselfin a class method, meaning it's attempting to callMatches.reject, which doesn't exist. You need to fetch records first, like this: