Rails 3.2如何将model.inspect转换为哈希？

Question

I'm capturing "point in time" (audit) data about certain model records using the inspect method to dump the state of the record to a string . For example after I've stored a User record in the variable a_user I call inspect and store the results in a string variable archived_user_data :

1.9.3p484 :045 > archived_user_data = a_user.inspect
 => "#<User id: 17, email: \"ray.johnson@breakfs.com\", encrypted_password: \"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....\", created_at: \"2014-04-05 21:42:09\", updated_at: \"2014-04-05 21:43:25\", account_id: 9>" 

1.9.3p484 :046 > archived_user_data
 => "#<User id: 17, email: \"ray.johnson@breakfs.com\", encrypted_password: \"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....\", created_at: \"2014-04-05 21:42:09\", updated_at: \"2014-04-05 21:43:25\", account_id: 9>" 

When the archived_user_data is retrieved sometime in the future, I need to convert it into a hash. Is there a simple way to do this? It looks like hashes converted to strings are usually converted back using eval , but in this case eval(archived_user_data) returns nil .

Answer 1

If you are still free to use Marshal, fine! If not, I suggest you peel down the string to the hash part using

s = archived_user_data.match(/#<User (.*)>/)[1]

after which you can reconstruct the hash using eval

eval("{" + s + "}")

Answer 2

Just do as below using attributes :

Returns a hash of all the attributes with their names as keys and the values of the attributes as values.

archived_user_data = a_user.attributes

Answer 3

You can use Marshal to dump and store any Ruby Object.

Example:

(Using reference from @Arup's code)

data_hash = a_user.attributes
dump_string = Marshal.dump(data_hash)
retrieved_hash = Marshal.load(dump_string)

You can store dump_string in file or database or in any other storage area.

EDIT

Specific case:

2.1.0 :013 > {:a => "b"}.inspect
 => "{:a=>\"b\"}"
2.1.0 :014 > "{id: 17, email: \"ray.johnson@breakfs.com\", encrypted_password: \"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....\", created_at: \"2014-04-05 21:42:09\", updated_at: \"2014-04-05 21:43:25\", account_id: 9}"
 => "{id: 17, email: \"ray.johnson@breakfs.com\", encrypted_password: \"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....\", created_at: \"2014-04-05 21:42:09\", updated_at: \"2014-04-05 21:43:25\", account_id: 9}"
2.1.0 :015 > eval("{id: 17, email: \"ray.johnson@breakfs.com\", encrypted_password: \"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....\", created_at: \"2014-04-05 21:42:09\", updated_at: \"2014-04-05 21:43:25\", account_id: 9}")
 => {:id=>17, :email=>"ray.johnson@breakfs.com", :encrypted_password=>"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....", :created_at=>"2014-04-05 21:42:09", :updated_at=>"2014-04-05 21:43:25", :account_id=>9}

You need to understand that hashes when inspected and stored as string aren't of the form:

"#<User id: 17, email: \"ray.johnson@breakfs.com\", encrypted_password: \"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....\", created_at: \"2014-04-05 21:42:09\", updated_at: \"2014-04-05 21:43:25\", account_id: 9>"

But should be of the form:

"{id: 17, email: \"ray.johnson@breakfs.com\", encrypted_password: \"$2a$10$v3CJZftIyDW/XZpktXXdMOuN1IxMoVmaofcIqEB6kBV....\", created_at: \"2014-04-05 21:42:09\", updated_at: \"2014-04-05 21:43:25\", account_id: 9}"

You can eval and get back the hash if you modify your string to the format above. Refer to my three line example above.