Replace hash value based on the value in another hash

Question

Given two hashes, I'm trying to replace a value in the first hash for a key that the second hash also has. To be specific, I have these two hashes:

data = {
  "study"       => "Lucid Study",
  "name"        => "Lucid Plan",
  "studyWillBe" => "Combination"
}

conditions = { "study" => "((current))" }

I want data to have its "study" key updated since conditions has that key. I want data to end up like this:

data = {
  "study"       => "((current))",
  "name"        => "Lucid Plan",
  "studyWillBe" => "Combination"
}

I got this far:

data = Hash[data.map {|k, v| [conditions[k] || k, v] }]

but that's not quite doing the trick. Can anyone point me in the right direction?

rohit89 · Accepted Answer · 2012-11-19 16:09:42Z

4

You can do this

data.each {|k, v| data[k] = conditions[k] if conditions[k]}

answered Nov 19, 2012 at 16:09

rohit89

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1 Comment

Jeff Nyman Over a year ago

This is perfect and does exactly what I need. Thank you very much for the quick response.

steenslag · Accepted Answer · 2012-11-19 16:16:46Z

2

It's called merge.

data = {"study"=>"Lucid Study", "name"=>"Lucid Plan", "studyWillBe"=>"Combination"}
conditions = {"study"=>"((current))"}

data.merge(conditions)
#{"study"=>"((current))", "name"=>"Lucid Plan", "studyWillBe"=>"Combination"}

answered Nov 19, 2012 at 16:16

steenslag

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1 Comment

sawa Over a year ago

This will give wrong result when conditions has a key that data doesn't.

megas · Accepted Answer · 2012-11-19 18:56:53Z

2

The method merge can take a block where you can make some specific operation not only assign new value

data.merge(conditions) do |key, oldvalue, newvalue|
  newvalue
end    
=> {"study"=>"((current))", "name"=>"Lucid Plan", "studyWillBe"=>"Combination"}

edited Nov 19, 2012 at 18:56

answered Nov 19, 2012 at 18:40

megas

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