Question

I have models called User, Activity, and Task and I can do the following

> puts Activity.joins(:task).to_sql
SELECT "activities".* FROM "activities" INNER JOIN "tasks" ON "tasks"."id" = "activities"."task_id" ORDER BY date DESC

> puts User.first.shared_tasks.to_sql
SELECT "tasks".* FROM "tasks" INNER JOIN "user_tasks" ON "tasks"."id" = "user_tasks"."task_id" WHERE "user_tasks"."user_id" = 1

但是,当我试图打上<条码>时,即。我收到了两个阵列:

> puts Activity.joins(:task).merge(User.first.shared_tasks).to_sql
NoMethodError: undefined method `to_sql  for []:Array

Why is that not returning a relation? I need to put a where clause on it.

最新情况:

在进行进一步检查后,将立即对<代码>User.first. Commond_tasks进行评价。我可以通过增加<条码><>条码/代码>来了解我所希望的行为。呼吁:

> puts Activity.joins(:task).merge(User.first.shared_tasks.order()).to_sql
SELECT "activities".* FROM "activities" INNER JOIN "tasks" ON "tasks"."id" = "activities"."task_id" INNER JOIN "user_tasks" ON "tasks"."id" = "user_tasks"."task_id" WHERE "user_tasks"."user_id" = 1 ORDER BY date DESC

除了增加一个空洞的<条码><>条码/代码>外,是否还有更好的办法防止这一关系得到评估?

Answer 1

诚然,我仍没有说明为什么要立即评价<代码>User.first. Commond_tas,但我已经做了一些工作。我只能打电话到<条码> 范围<>。

> User.first.shared_tasks.class
=> Array

> User.first.shared_tasks.scoped.class
=> ActiveRecord::Relation

Now when I try to do the merge:

Activity.joins(:task).merge(User.first.shared_tasks.scoped)

它使用<条码>活性记录:Relation#mer,而不是Array#mer。

Answer 2

Whenever you call a method on a relation object that it doesn t respond to, it delegates that method to some other type of object. In the case of merge, it will be converted to an array. This is done via the ActiveRecord::Delegation module. Some methods such as each are explicitly delegated, and others such as merge are done through method_missing.

例如,如果是:

Activity.joins(:task).each { |activity| puts activity }

联系代表<代码>.each到一个阵列(计算器),基本上进行转换。

Answer 3

为了与你的关系,你可以尝试这样做。

puts (Activity.joins(:task) & User.first.shared_tasks).to_sql

合并有助于形成一个范围,并归还一系列已实现的目标。

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