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Rails 3 - Looping through DB records, one record has a HASH

Answer 1

+1 A:

If you have a list of results like this you would do something like the following:

@results.each do |result|
  p result.data.photoId
end

You can certainly get fancier but hopefully this will get you along for now.

Chuck Vose 2010-09-30 02:14:38

That's incredible,,, bonus point for if you can share how to store the data field like it is above. thanks!

WozPoz 2010-09-30 02:16:40

Probably just need to marshall the data before it goes into the database. Check out this link: http://api.rubyonrails.org/classes/ActiveRecord/Base.html specifically the section on saving arrays and hashes. Excellent guide.

Chuck Vose 2010-09-30 02:35:37

@Chuck, just tried the above and it errors? does the p in the front have any significance? I tried it w and w/o and both failed... The error I get is "NoMethodError" undefined method `photo_id' for #<String:0x1033a80f0>

WozPoz 2010-09-30 02:53:26

Use `result.data['photoID']` to index into a Hash object in Ruby.

Raphomet 2010-09-30 03:19:51

@raphomet thanks... I just tried that and it just outputs photoID and not the value in the DB meta field data? I tried it without the ' so just [photoID] and it errors: undefined local variable or method `photoID'

WozPoz 2010-09-30 03:23:12

Am I storing it in the database correctly? {photoID:2089, photoName: "blah"}

WozPoz 2010-09-30 03:24:19

It looks like you converted a JavaScript Object into a string and saved it. You might have to cast into a Ruby Hash after fetching it out of the database: `JSON.parse(result.data)['photoID']`

Raphomet 2010-09-30 03:35:25

So here's the deal... I haven't built the part that stores the data yet, and that won't be JSON based. How should the data look in data field to be a Ruby HASH?

WozPoz 2010-09-30 03:38:13

Woz, I apologize but I have to go to bed. @raph, thanks for the correction.

Chuck Vose 2010-09-30 03:48:11

Make the database column a string. Marshal (which means to serialize a data object into a string) the data using `Marshal.dump(data)`. When you fetch it back out of the database, you can convert it back into a Hash using `Marshal.load(data)`.

Raphomet 2010-09-30 03:54:52

@Raphomet interesting, I have not heard of the ability to Marshal, google searching to learn more and try it out. Not finding much, know of any tutorials or examples so I can understand the suggestion? or would it be possible to see an example Marshal.dump and load,, and what the data would look like for the above in the database for 1 field? thanks

WozPoz 2010-09-30 04:12:33

What about YAML?

WozPoz 2010-09-30 04:26:54

Marshaling is dangerous, as it may not be interoperable, and it may differ depending on ruby Ruby version. I preffer YAML or JSON - data lasts longer than applications.

gertas 2010-09-30 06:51:55

I think I'm going to go with JSON, seems pretty simple to use... Anyone know about the JSON performance?

WozPoz 2010-09-30 14:59:28

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Rails 3 - Looping through DB records, one record has a HASH

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