Delegate default value option

rubyonrails-core
1

I find I often use delegate and many nil guards in my facades. Adding a default_value option to delegate would simplify this, but I am interested how others feel about it.

Implementation would look something like:

class PersonFacade

delegate :name, :to => :person, :default_value => “”

def initialize(person)

@person = person

end

end

p = Person.find

p.name => nil

f = PersonFacade.new(p)

f.name => “”

1 Like
2

I like this idea and would use it.

-Amiel

3

Thanks.

I will work up a pull request and see if I can get it added.

4

What is the advantage over?

def name
  [person.name](http://person.name) || ""
end

I am really against adding new options to delegate method since all that it does is define methods like this in the class.

5

It’s not clear (to me) how this should interact with passing multiple attributes to delegate:

delegate :foo, :bar, :baz, :to => :person

Also, should the default value be returned if :allow_nil is set and the delegated-to object isn’t present?

–Matt Jones

6

This is why I wanted to ask the group before making the pull request.

As for Rafael’s question – it is no different from writing the methods out, but either is delegate. I just found that many times where I would have used delegate I ended up writing out the individual methods only to add || = “”. So, I thought others might use it as well.

As for Matt’s questions:

(1) It’s not clear (to me) how this should interact with passing multiple attributes to delegate:

The way I wrote it all of the delegated methods passed would get the default values so:

delegate :foo, :bar, :to => :person, :default_value => “”

delegate :baz, :to => :person

foo => “”

bar => “”

baz => nil

(2) Also, should the default value be returned if :allow_nil is set and the delegated-to object isn’t present?

Yes.

7

We already rejected this feature before. See https://github.com/rails/rails/pull/11908

8

Fair enough, thanks for the reference.