First the problem:
I'm writing a load test framework at work and I need to consume JSON webservice and pass on the output to another request. But I don't always know what the data is that I need to pass on but I do know the basic "path" ("hpath" -- "hash path") to get to the data as the JSON data is uniform.
Now the method:
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# Picks out data from a (JSON) decoded hash based on the @passon hash,
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# which looks like this:
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# { "id" => "packet.products[0].attributes.id",
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# "quantity" => "packet.products[0].attributes.quantity"
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# }
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# The "id" and "quantity" are the new keys for the return data;
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# packet.products[0].attributes.id will look at the value of the id key
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# in the attributes hash in the 0th element of the products array in the
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# packet hash.
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def pick_out_passon(hash_data)
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return {} unless @passon
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returnhash = {}
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nh = hash_data.dup
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@passon.each do |newkey,part_str|
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parts = part_str.split(".").reverse
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while (part = parts.pop) do
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m = part.match(/\[(\d+)\]/)
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index = nil
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if m
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index = m[1].to_i
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part.gsub!(/\[#{m[0]}\]/,'')
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end
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nh = nh.values_at(part).first
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nh = nh.at(index) if index
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end
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returnhash.merge!({ newkey=> nh})
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nh = hash_data.dup
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end
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returnhash
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end
What's it do? It does magic!
I'll step through it...
Looks for @passon instance variable and doesn't do anything useful unless it exists.
Duplicate the input hash because the process done is destructive to it and we may need to reuse it.
For each new hash key and "hpath" pair from @passon split up the hpath into its parts and reverse it so Array#pop will work in the while loop to get the next first part to try.
Since each part of the hpath can examine an Array by index it has to be checked for and the index removed from the part (and saved).
Next, investigate the copy of the hash_data, nh by the computed key; if the value in the hash was an Array use the index to get the desired value. Then compute the next part!
Once we're out of parts stuff the new key and data into the returnhash and keep going til there's no more @passon pairs.
And thus some fun code was written.
