Squeel evaluating a string as a keypath for joins

问题

Here's what I'd really like to do:

Outage.joins{eval "unit.plant"}

I'm going to have a string that represents a squeel keypath. I'd like to send this string into a join statement.

But here's what I get as an error:

#<Class:0x639e328>: unknown class: Squeel::Nodes::Function

I've tried:

Outage.joins{"unit.plant"}

But that does not work... what am I missing?

I don't see any documentation on this on the github page: https://github.com/ernie/squeel/

Thank you for any help!

Update: I've found a really confusing way to pull this off:

("unit.plant".split ".").map{ |x| x.to_sym }.reverse.inject{ |acc, x| { x => acc } }

This will output:

{:unit=>:plant}

This can be passed into the joins squeel function. I'm sure there has to be a better way than to construct nested symbols :(

回答1:

How about

Outage.joins{Squeel::Nodes::KeyPath.new("unit.plant".split("."))}

Source: KeyPath Docs

回答2:

Alternative solution, it can be chained with outer/inner:

strs = "unit.plant"
Outage.joins{strs.split(".").inject((strs.present? ? self : nil), :__send__)}

# chain with inner
# Outage.joins{strs.split(".").inject((strs.present? ? self : nil), :__send__).inner}

来源：https://stackoverflow.com/questions/11641802/squeel-evaluating-a-string-as-a-keypath-for-joins