How do I pretty print a hash to a Rails view?

Question

I have something like:

{"a":"1","b":"2","c":"3","asefw":"dfsef"}

I want to print it out in a view. What's the best way to do that?

I tried parsing it as a JSON object and using JSON.stringify, but it seems to mess up indentation.

Any advice? I don't mind a JavaScript solution.

You're making us guess what you want, which is no fair. We can't guess because they suspended our mind-reading abilities. Can we buy a clue? — the Tin Man, Jun 25 '13 at 05:09
Code prettyfiers for a possible JavaScript solution: http://stackoverflow.com/questions/160694/syntax-highlighting-code-with-javascript — Casper, Jun 25 '13 at 05:31

the Tin Man · Answer 1 · 2013-06-25T05:19:21.077

23

How about:

require 'json'

hash = JSON['{"a":"1","b":"2","c":"3","asefw":"dfsef"}']
puts JSON.pretty_generate(hash)

Which outputs:

{
  "a": "1",
  "b": "2",
  "c": "3",
  "asefw": "dfsef"
}

JSON.pretty_generate is more of a debugging tool than something I'd rely on when actually generating JSON to be sent to a browser. The "pretty" aspect also means "bloated" and "slower" because of the added whitespace, but it is good for diagnosing and comprehending what is in the structure so it might work well for your needs.

One thing to remember is that HTML, when rendered by a browser, has whitespace gobbled up, so whitespace runs disappear. To avoid that you have to wrap the JSON output in a <pre> block to preserve the whitespace and line-breaks. Something like this should work:

<pre>
{
  "a": "1",
  "b": "2",
  "c": "3",
  "asefw": "dfsef"
}
</pre>

edited Jun 25 '13 at 05:19

answered Jun 25 '13 at 05:14

the Tin Man

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I disagree, if your product is an API that developers will be using then clean JSON can be a blessing for them and with gzip compression the added whitespace isn't much of a burden. Either way, would be nice to have an option to pretty print or not within your API. – Nov 16 '14 at 20:23
We use browser plugins that allow us to see "prettitifed" JSON when we look at the output of our code while debugging, but the code itself outputs standard JSON. Between apps there is no point in sending the extra space since they don't care. Only humans do, so the browser plugins keep us happy. – the Tin Man Nov 17 '14 at 16:48
JSON's inherent lack of DATE support makes using JSON bad if your hash includes dates... you will not be able to tell by looking if an object is a 'real' date or a stringified date since JSON will always stringify it. – jpw Jul 15 '17 at 20:09

score 6 · Answer 2 · edited Jul 17 '20 at 22:24

6

irb(main)> puts queried_object.pretty_inspect

From PrettyPrint, so may need to require 'pp' first for this to work.

This also works great for e.g. Rails.logger output.

edited Jul 17 '20 at 22:24

pdobb

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answered Sep 19 '16 at 17:52

hophacker

61
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2

score 3 · Answer 3 · answered Oct 12 '13 at 21:21

3

<%= raw JSON.pretty_generate(hash).gsub(" ","&nbsp;") %>

answered Oct 12 '13 at 21:21

Amol Pujari

2,280
20
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score 3 · Answer 4 · answered Apr 16 '15 at 15:54

If you (like I) find that the pretty_generate option built into Ruby's JSON library is not "pretty" enough, I recommend my own NeatJSON gem for your formatting.

To use it gem install neatjson and then use JSON.neat_generate instead of JSON.pretty_generate.

Like Ruby's pp it will keep objects and arrays on one line when they fit, but wrap to multiple as needed. For example:

{
  "navigation.createroute.poi":[
    {"text":"Lay in a course to the Hilton","params":{"poi":"Hilton"}},
    {"text":"Take me to the airport","params":{"poi":"airport"}},
    {"text":"Let's go to IHOP","params":{"poi":"IHOP"}},
    {"text":"Show me how to get to The Med","params":{"poi":"The Med"}},
    {"text":"Create a route to Arby's","params":{"poi":"Arby's"}},
    {
      "text":"Go to the Hilton by the Airport",
      "params":{"poi":"Hilton","location":"Airport"}
    },
    {
      "text":"Take me to the Fry's in Fresno",
      "params":{"poi":"Fry's","location":"Fresno"}
    }
  ],
  "navigation.eta":[
    {"text":"When will we get there?"},
    {"text":"When will I arrive?"},
    {"text":"What time will I get to the destination?"},
    {"text":"What time will I reach the destination?"},
    {"text":"What time will it be when I arrive?"}
  ]
}

It also supports a variety of formatting options to further customize your output. For example, how many spaces before/after colons? Before/after commas? Inside the brackets of arrays and objects? Do you want to sort the keys of your object? Do you want the colons to all be lined up?

For example, using your example Hash, you can get these different outputs, depending on what you want:

// JSON.neat_generate(o, wrap:true)
{
  "a":"1",
  "b":"2",
  "c":"3",
  "asefw":"dfsef"
}

// JSON.neat_generate o, wrap:true, aligned:true
{
  "a"    :"1",
  "b"    :"2",
  "c"    :"3",
  "asefw":"dfsef"
}

// JSON.neat_generate o, wrap:true, aligned:true, around_colon:1
{
  "a"     : "1",
  "b"     : "2",
  "c"     : "3",
  "asefw" : "dfsef"
}

score 3 · Answer 5 · answered Oct 26 '17 at 15:38

3

You can try the gem awesome_print works very well, and in your view write

<%= ap(your_hash, plain: true, indent: 0).html_safe %>

also, you can change the values for config the styles to hash view

answered Oct 26 '17 at 15:38

Daniel Arenas

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score 2 · Answer 6 · answered Jun 25 '13 at 10:19

2

The given response is works fine, but if you want to have prettier and more custom pretty hash, use awesome_print

require 'awesome_print'
hash = JSON['{"a":"1","b":"2","c":"3","asefw":"dfsef"}']
ap hash

Cheers!

answered Jun 25 '13 at 10:19

Belkacem REBBOUH

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awesome_print has the unfortunate flaw of forcing alignment of hashes so the => value is aligned whcih doe snot work well for nested hashes (nested hash value are actually displayed to the LEFT of the parent hash values). – jpw Jul 15 '17 at 20:07

score 1 · Answer 7 · answered Jul 17 '21 at 08:55

Pretty Print Hash using pure Ruby (no gems)

I came across this thread trying to solve this problem for myself.

I had a large Hash that I wanted to make pretty, but I needed to stay in ruby hash notation instead of JSON.

This is the code + examples

Use pretty_generate to get a nice formatted JSON string.
Replace all the JSON keys with symbol: equivalent

puts JSON.pretty_generate(result)
         .gsub(/(?:\"|\')(?<key>[^"]*)(?:\"|\')(?=:)(?:\:)/) { |_|
              "#{Regexp.last_match(:key)}:"
          }

Sample JSON

{
  "extensions": {
    "heading": "extensions",
    "take": "all",
    "array_columns": [
      "name"
    ]
  },
  "tables": {
    "heading": "tables",
    "take": "all",
    "array_columns": [
      "name"
    ]
  },
  "foreign_keys": {
    "heading": "foreign_keys",
    "take": "all",
    "array_columns": [
      "name"
    ]
  },
  "all_indexes": {
    "heading": "all_indexes",
    "take": "all",
    "array_columns": [
      "name"
    ]
  },
  "keys": {
    "heading": "keys",
    "take": "all",
    "array_columns": [
      "name"
    ]
  }
}

Sample Ruby Hash

{
  extensions: {
    heading: "extensions",
    take: "all",
    array_columns: [
      "name"
    ]
  },
  tables: {
    heading: "tables",
    take: "all",
    array_columns: [
      "name"
    ]
  },
  foreign_keys: {
    heading: "foreign_keys",
    take: "all",
    array_columns: [
      "name"
    ]
  },
  all_indexes: {
    heading: "all_indexes",
    take: "all",
    array_columns: [
      "name"
    ]
  },
  keys: {
    heading: "keys",
    take: "all",
    array_columns: [
      "name"
    ]
  }
}

How do I pretty print a hash to a Rails view?

7 Answers7