How to handle JSON parser errors in ruby

Question

How do I avoid parsing JSON if the response body will not be in JSON, else it throws a huge exception which I would like to handle

      def execute_method(foo)
...

        response = self.class.get("/foo.php", query: query)
        JSON.parse(response.body)
      end

I don't want to parse, I would like to find out before parsing. How should I do that? — Rpj
– Rpj, Commented Jan 16, 2015 at 12:05

Magnuss · Accepted Answer · 2018-11-29 05:42:58Z

59

As @Anthony pointed out, use begin/rescue.

begin
  ...
  JSON.parse(response.body)
rescue JSON::ParserError
  # Handle error
end

Update

To check if a string is a valid json, you can create a method:

def valid_json?(string)
  !!JSON.parse(string)
rescue JSON::ParserError
  false
end

valid_json?("abc") #=> false
valid_json?("{}") #=> true

edited Nov 29, 2018 at 5:42

answered Jan 14, 2015 at 13:48

Magnuss

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2 Comments

Rpj Over a year ago

I don't want to parse, I would like to find out before parsing. How should I do that?

Magnuss Over a year ago

@Rpj I added a method to check if string is a valid json. I don't think there is any other way to be absolutely sure, other than trying to successfully parse it.

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