Best practise for setting default URL parameters in the controller

rubyonrails-talk
1

I’ve been trying to set default URL parameters in the controller, which will also be used within the view. This is what I’ve got:

@params = params

defaults = { :date_from => ‘21/1/21014’, :date_to => ‘21/2/21014’, :data=>“Expense” } if @params.any? @params = defaults.merge(@params) else @params = defaults end

… seems messy, and doesn’t work :frowning: When params are present it still uses the default params. Not sure where it’s going wrong and search on google yields many varieties. I know using default values in methods is something that I will repeat again so I was wondering what the best practise is for handling this. Thanks

2

That is likely because it should be params not @params. I don't think you need the .any? test either, just let it merge the empty hash into defaults.

If you need to do this in more than one controller method then use a before filter.

Colin

3

It doesn't work because @params isn't where params are stored. Params is never empty (at a minimum :controller and :action are set) so you can get rid of the else

You could update params in place , ie params.merge!(...).

Personally I wouldn't do this. I'd be more likely to have a controller method called something like get_date_range that would get the dates from params that would do things like parse the strings into actual dates and/or replace missing params with defaults.

Fred

4

... You could update params in place , ie params.merge!(...).

Would that not use the value from defaults if it was already present in params?

Personally I wouldn't do this. I'd be more likely to have a controller method called something like get_date_range that would get the dates from params that would do things like parse the strings into actual dates and/or replace missing params with defaults.

+1

Colin

5

> ...

> You could update params in place , ie params.merge!(...).

Would that not use the value from defaults if it was already present in params?

I was assuming this was after checking that params didn't have the values in question, although if not you could use reverse_merge!

Fred

6

That is likely because it should be params not @params.

But:

....

This is what I've got:

@params = params

so @params should work the same as params. Not sure why he's bothering to copy it into an @-var, tho; maybe he wants access to it in a view....

-Dave

7

Personally, I'd say "best practice" is "don't do that" :slight_smile:

Instead of passing raw params to a view, build your model object (or a service object) with them and pass that in. And if you need defaults for missing attributes specified, the model/s.o. would be a better place for them.

FWIW,