我第一次尝试元编程,但进展不太顺利!这是一个Rails4.1应用程序,我正在尝试重构一个活动记录模型(User),以将两种非常相似的方法结合起来。最初的方法是稍微复杂的DB调用,并按预期工作。
原始代码:
def retweet_count(league)
celebrity_ids = Roster.
where("user_id = ? and league_id = ?", self.id, league.id).
select(:celebrity_id).map { |r| r.celebrity_id }
Tweet.where({
tweet_date: league.start_date..league.end_date,
celebrity_id: celebrity_ids
}).select(:retweet_count).inject(0) do |sum, n|
sum + ( n.retweet_count || 0 )
end
end
def favorite_count(league)
celebrity_ids = Roster.
where("user_id = ? and league_id = ?", self.id, league.id).
select(:celebrity_id).map { |r| r.celebrity_id }
Tweet.where({
tweet_date: league.start_date..league.end_date,
celebrity_id: celebrity_ids
}).select(:favorite_count).inject(0) do |sum, n|
sum + ( n.favorite_count || 0 )
end
end
新代码:
twitter_stats_count :retweet, :favorite
private
def twitter_stats_count(*stats)
stats.each do |statistic|
stat = send(statistic).to_s
define_method "#{stat}_count" do |league|
celebrity_ids = Roster.
where("user_id = ? and league_id = ?", self.id, league.id).
select(:celebrity_id).map { |r| r.celebrity_id }
Tweet.where({
tweet_date: league.start_date..league.end_date,
celebrity_id: celebrity_ids
}).select("#{stat}_count").inject(0) do |sum, n|
sum + ( n.send("#{stat}_count") || 0 )
end
end
end
end
当我尝试启动rails服务器时,新代码产生的错误:
/Users/kiddo/.rvm/gems/ruby-2.1.0/gems/activerecord-4.1.0.rc2/lib/active_record/dynamic_matchers.rb:26:in `method_missing': undefined method `twitter_stats_count' for User (call 'User.connection' to establish a connection):Class (NoMethodError)
我似乎不明白自己做错了什么,所以任何建议都将不胜感激!
仅供参考,这是我工作的最后一个代码。我主要接受了Holger Just的建议,但结合了其他几个方面的建议,所以周围都投了赞成票!
def team_ids(league)
Roster.where(user_id: self.id, league_id: league.id).pluck(:celebrity_id)
end
def self.twitter_stats_count(*stats)
stats.each do |statistic|
stat = statistic.to_s
define_method "#{stat}_count" do |league|
Tweet.where({
tweet_date: league.start_date..league.end_date,
celebrity_id: self.team_ids(league)
}).sum("#{stat}_count")
end
end
end
twitter_stats_count :retweet, :favorite
您的方法有几个问题:
-
直接在类上调用
twitter_stats_count
,而不是在类的实例上调用。因此,该方法需要是一个类方法。您可以将其定义为具有的类方法def self.twitter_stats_count(*stats) # ... end
-
此外,在定义该方法之前,您需要调用该方法。在Ruby中,一切(甚至方法定义)都是执行的。因此,您只能在定义方法之后才能调用它们。因此,您需要将对
twitter_stats_count
方法的调用放在其定义之后。
这看起来相当复杂。如果我没有错的话,你可以通过重构你的代码来减少重复:
def retweet_count(league)
league_tweets(league).sum(:retweet_count)
end
def favorite_count(league)
league_tweets(league).sum(:favorite_count)
end
def celebrity_ids(league)
Roster.where(user_id: self.id, league_id: league.id).pluck(:celebrity_id)
end
def league_tweets(league)
Tweet.where(
tweet_date: league.start_date..league.end_date,
celebrity_id: celebrity_ids(league)
)
end
twitter_stats_count应该是一个类方法,但您所做的是将其作为一个实例方法,也许您可以尝试一下:
# no private here
def self.twitter_stats_count(*status)
#your codes here
end
您得到这个错误是因为,您已经将twitter_stats_count
定义为私有方法,您不能在self
上调用它。你必须把它放在一个实例方法中,而不是调用它
检查一下。
例如,下面给出了相同的错误:
class Foo
baz
private
def baz
puts "baz called"
end
end
然而,这将起作用:
class Foo
def dummy
baz
end
private
def baz
puts "baz called"
end
end
foo = Foo.new
foo.dummy