ruby on rails - How to validate the presence of attributes when updating a record? -

i new rails , try find validation method corresponding validate presence of attribute when updating record. if attribute not present, meaning attribute not exist request body, rails should not update record.

validates :description, presence: true 

and

validates_presence_of :description 

doesn't seem job. there method purpose? seems quite common in every day scenarios.

if say:

model.update(hash_that_has_no_description_key) 

then you're not touching :description: sending hash without :description key update not same sending in hash :description => nil. if model valid (i.e. has description) update won't invalidate because won't touch :description.

you this:

if attribute not present, meaning attribute not exist request body, rails should not update record.

since you're talking request body (which models shouldn't know about) should dealing logic in controller prepares incoming data update call.

you check in controller , complain:

data = whatever_params if(!data.has_key?(:description))   # complain in appropriate manner... end # continue now... 

or include :description => nil if there no :description:

def whatever_params   data = params.require(...).permit(...)   data[:description] = data[:description].presence # or prefer this...   data end