Arel: How to cleanly join multiple conditions with OR?

问题

In my Rails app, I loop through an array to create a list of conditions that must be joined by OR. Below is the basic flow of how I currently do so.

conditions = nil
set.each do |value|
  condition = value.to_condition
  conditions = conditions ? conditions.or(condition) : condition
end

Obviously, it's not beautiful, but I still don't fully know my way around Arel. Does it offer any better way of OR-joining a set of dynamically-generated conditions?

回答1:

This is a perfect fit for an inject which will give you a one-liner you can use within something else as well: conditions = set.inject { |conds, cond| conds.or(cond) } which can even be written: set.inject(&:or) which is very nice.

回答2:

There is also a useful plugin for this.

conditions_helper

It helps to generate complex conditions.

回答3:

I think that's basically it. I'd initialize conditions to the base object to avoid the ternary:

scope = Article
set.each{|v| scope = scope.or(v.to_condition)}

来源：https://stackoverflow.com/questions/2992393/arel-how-to-cleanly-join-multiple-conditions-with-or