Why can Ruby not parse local JSON file?

问题

I have a related question here, but I'm posting another question to focus on a specific part of the problem.

Goal: Add script to my Ruby app which can read a local JSON file, parse it to a Ruby hash, and access the properties within it.

System: CentOS 7

File: Locally saved /tmp/valid.json file:

{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 27,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    }
  ],
  "children": [],
  "spouse": null
}

(That object borrowed from Wikipedia's article on JSON in an attempt to make sure that my problem isn't invalid JSON.)

Code:

require 'json'
data = File.read("/tmp/valid.json")
$evm.log(:info, data) #writes to log file, where I can see content of my JSON file
$evm.log(:info, "is data a hash ? ")
$evm.log(:info, data.is_a?(Hash).to_s) # prints false
$evm.log(:info, "is data a string? ")
$evm.log(:info, data.is_a?(String).to_s) # prints true
$evm.log(:info, "can I parse data?")
valid_ob = JSON.parse(data)
$evm.log(:info, "just parsed it, now print it")
$evm.log(:info, valid_ob)

That last line prints:

NoMethodError: undefined method `gsub' for #<Hash:0x0000000020951f
a8>

Why can't Ruby parse this string?

回答1:

The problem is something in whatever you have assigned to $evm. The error message:

NoMethodError: undefined method `gsub' for #<Hash:>

indicates that when you call

$evm.log(:info, valid_ob)

the log method is attempting to call gsub on valid_ob. Most likely, log is meant to accept only strings and does no type checking on the object it receives.

If you need a simple, interactive way to run this Ruby code without using this $evm object, just run irb in your console and start typing in your Ruby code for parsing the JSON data:

require 'json'
 => true
data = File.read('/tmp/valid.json')
data.class
 => String
hash = JSON.parse(data)
hash.class
 => Hash
hash
 => {"firstName"=>"John", "lastName"=>"Smith", "isAlive"=>true, "age"=>27, "address"=>{"streetAddress"=>"21 2nd Street", "city"=>"New York", "state"=>"NY", "postalCode"=>"10021-3100"}, "phoneNumbers"=>[{"type"=>"home", "number"=>"212 555-1234"}, {"type"=>"office", "number"=>"646 555-4567"}], "children"=>[], "spouse"=>nil}

回答2:

Have you tried printing the object normally, instead of using "$evm.log"? JSON.parse returns a hash, and it seems as though your logger is attempting to run a non-existent gsub method on it.

来源：https://stackoverflow.com/questions/63748477/why-can-ruby-not-parse-local-json-file

标签

json

ruby

file

parsing