Why does this rescue syntax work?

Question

Ok so I have this method of an application I am working with and it works in production. My question why does this work? Is this new Ruby syntax?

def edit
  load_elements(current_user) unless current_user.role?(:admin)

  respond_to do |format|
    format.json { render :json => @user }   
    format.xml  { render :xml => @user }
    format.html
  end

rescue ActiveRecord::RecordNotFound
  respond_to_not_found(:json, :xml, :html)
end

See also http://stackoverflow.com/questions/1542672/how-does-one-use-rescue-in-rails-without-the-begin-and-end-block — Lars Haugseth, Apr 10 '12 at 13:06

score 13 · Accepted Answer · edited May 23 '17 at 12:14

13

rescues do not need to be tied to an explicit begin when they're in a method, that's just the way the syntax is defined. For examples, see #19 here and this SO question, as well as the dupe above.

edited May 23 '17 at 12:14

Community

1
1

answered Apr 10 '12 at 13:06

Dave Newton

158,873
26
254
302

score 2 · Answer 2 · answered Apr 10 '12 at 13:11

2

rescue can work alone . no need of begin and end always .

You can use rescue in its single line form to return a value when other things on the line go awry:

h = { :age => 10 }
h[:name].downcase                         # ERROR
h[:name].downcase rescue "No name"

answered Apr 10 '12 at 13:11

Vik

5,931
3
31
38

This uses it as a statement modifier, though, which isn't the OP's question. You're correct, of course, but it doesn't directly answer the question. – Dave Newton Apr 10 '12 at 13:13

score 0 · Answer 3 · answered Apr 10 '12 at 12:57

0

rescue word is part of method definition

But in controllers better to rescue errors with rescue_from

answered Apr 10 '12 at 12:57

mikdiet

9,859
8
59
68

score -3 · Answer 4 · answered Apr 10 '12 at 13:01

-3

try this

def edit
  begin
    load_elements(current_user) unless current_user.role?(:admin)

    respond_to do |format|
      format.json { render :json => @user }   
      format.xml  { render :xml => @user }
      format.html
    end

  rescue ActiveRecord::RecordNotFound
    respond_to_not_found(:json, :xml, :html)
  end
end

answered Apr 10 '12 at 13:01

dku.rajkumar

18,414
7
41
58

It's perfectly legal to use a `rescue` inside a method definition (and implicit `begin`) without an explicit `begin`. – Dave Newton Apr 10 '12 at 13:11

Why does this rescue syntax work?

4 Answers4

Linked