Rails using a variable on left side of where clause

Question

I am looking to do the following:

var = 'bank_id'
id = '100'

Bank.where(var: id) or
Bank.where("? = ?", var, id)

Bank is a model. bank_id is an attribute of the model and it is taking it as a string.

Answer 1

Where does accept a hash witch gets mapped to the correct SQL WHERE.

Bank.where(var: id)

is actually

Bank.where({:var => id})

So you can construct your own hash key:

Bank.where({ var.to_s => id })

Or shorter:

Bank.where(var => id)

Just to clarify: The difference actually lies in the different syntax for hash. There are basically two versions.

1. The old "Hash-Rocket" syntax { key => value } actually accepts anything as key.
2. The new JSON style always uses symbols als keys and thus var does not get interpreted as a variable but as the symbol :var.

Always coding has a more detailed explanation.