Fetch the Hash from a string

Sadaf_N · August 26, 2013, 9:42pm

require ‘json’

str = “1=2,3=(4=5,6=7)”
new_str = str.gsub(/=|(|)/) do |m|
if m == “=”
m= “=>”
elsif m == “(”
m = “{”
else
m = “}”
end
end

new_str = new_str.prepend("{") << “}”

=> “{1=>2,3=>{4=>5,6=>7}}”

JSON.parse(new_str)

~>

/home/kirti/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/json/common.rb:155:in
`parse’: 757: unexpected token at ‘{1=>2,3=>{4=>5,6=>7}}’
(JSON::ParserError)

~> from

/home/kirti/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/json/common.rb:155:in
`parse’

~> from -:15:in `’

My question is how should I get the hash {1=>2,3=>{4=>5,6=>7}} from that
string?

my-ruby · August 26, 2013, 9:59pm

On Mon, Aug 26, 2013 at 12:42 PM, Love U Ruby [email protected]
wrote:

My question is how should I get the hash {1=>2,3=>{4=>5,6=>7}} from that
string?

Why don’t you generate valid JSON in the first place?

{1=>2,3=>{4=>5,6=>7}}.to_json would show you what the string
should look like (and why your example is so broken).

–
Hassan S. ------------------------ [email protected]

twitter: @hassan

my-ruby · August 26, 2013, 10:12pm

Hassan S. wrote in post #1119612:

On Mon, Aug 26, 2013 at 12:42 PM, Love U Ruby [email protected]
wrote:

My question is how should I get the hash {1=>2,3=>{4=>5,6=>7}} from that
string?

Why don’t you generate valid JSON in the first place?

{1=>2,3=>{4=>5,6=>7}}.to_json would show you what the string
should look like (and why your example is so broken).

In my case the hash is inside the string,but I want the hash back from
the string? I don’t know how to do this…

my-ruby · August 26, 2013, 10:40pm

On Mon, Aug 26, 2013 at 1:12 PM, Love U Ruby [email protected]
wrote:

In my case the hash is inside the string,but I want the hash back from
the string? I don’t know how to do this…

If you must use that format –

2.0.0-p247 :017 > str
=> “1=2,3=(4=5,6=7)”
2.0.0-p247 :018 > eval
str.tr(‘()’,‘{}’).gsub(/=/,‘=>’).prepend(‘{’).concat(‘}’)
=> {1=>2, 3=>{4=>5, 6=>7}}
2.0.0-p247 :019 >

–
Hassan S. ------------------------ [email protected]

twitter: @hassan

my-ruby · August 26, 2013, 11:08pm

On Aug 26, 2013, at 2:42 PM, Love U Ruby [email protected] wrote:

end

~> from

/home/kirti/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/json/common.rb:155:in
`parse’

~> from -:15:in `’

My question is how should I get the hash {1=>2,3=>{4=>5,6=>7}} from that
string?

There is no JSON here at all.

Given this:

new_str = new_str.prepend(“{”) << “}”

=> “{1=>2,3=>{4=>5,6=>7}}”

You have a string which represents a what a Hash looks like. Why not run
it through eval and see what you get?

my_hash = eval(new_str)

my-ruby · August 26, 2013, 11:10pm

tamouse m. wrote in post #1119628:

On Aug 26, 2013, at 2:42 PM, Love U Ruby [email protected] wrote:

You have a string which represents a what a Hash looks like. Why not run
it through eval and see what you get?

my_hash = eval(new_str)

I was trying to avoid eval. I tried also the yaml. But no luck

my-ruby · August 27, 2013, 2:43am

On 2013-Aug-26, at 17:10 , Love U Ruby wrote:

tamouse m. wrote in post #1119628:

On Aug 26, 2013, at 2:42 PM, Love U Ruby [email protected] wrote:

You have a string which represents a what a Hash looks like. Why not run
it through eval and see what you get?

my_hash = eval(new_str)

I was trying to avoid eval. I tried also the yaml. But no luck

If all your keys and values are just digits (i.e., String#to_i likes
them), then you can easily avoid eval and yaml. Just make your own
parser. Here are some “learning tests” to get you started. If you avoid
scrolling down too far to see my “answer”, then just make the tests pass
and you’re done!

Of course, you can also expand the tests to cover even more exotic hash
keys and values, but if you go too far you’ve just reinvented YAML or
JSON with different syntax.

-Rob

require ‘minitest/autorun’

class TestSomeCrappyMarkupLanguage < Minitest::Test
def setup
@str = “1=2,3=(4=5,6=7)”
end

def test_nil
refute SomeCrappyMarkupLanguage.parse(nil)
end

def test_empty_string
assert_equal({}, SomeCrappyMarkupLanguage.parse(“”))
end

def test_simple_hash
assert_equal({1=>2}, SomeCrappyMarkupLanguage.parse(“1=2”))
end

def test_two_elements
assert_equal({4=>5,6=>7}, SomeCrappyMarkupLanguage.parse(“4=5,6=7”))
end

def test_nested
expected = { 1 => 2, 3 => { 4 => 5, 6 => 7 } }
assert_equal expected, SomeCrappyMarkupLanguage.parse(@str)
end

end

spoilers below…

class SomeCrappyMarkupLanguage
def self.parse(str)
return nil unless str
result = {}
str.scan(/(\d+)=((?:([^)]*))|\d+),?/).each do |key,value|
key = key.to_i
value = value =~ /\A\d+\z/ ? value.to_i : parse(value)
result[key] = value
end
result
end
end

my-ruby · August 27, 2013, 9:55am

Rob B. wrote in post #1119642:

@Rob - thanks for such an detailed answer… I need to give some more
time on this…

class SomeCrappyMarkupLanguage
def self.parse(str)
return nil unless str
result = {}
str.scan(/(\d+)=((?:([^)]*))|\d+),?/).each do |key,value|
key = key.to_i
value = value =~ /\A\d+\z/ ? value.to_i : parse(value)
result[key] = value
end
result
end
end