From: Daniel Schierbeck <daniel.schierbeck@...>
Date: 2006-06-20T17:49:34+09:00
Subject: Re: associative array naming indirection

Berger, Daniel wrote:
>> -----Original Message-----
>> From: Daniel Schierbeck [mailto:daniel.schierbeck@gmail.com] 
>> Sent: Monday, June 19, 2006 2:36 PM
>> To: ruby-talk ML
>> Subject: Re: associative array naming indirection
>>
>>
>> dan donaldson wrote:
>>> I have an array of names in string form as an instance var. 
>> The class
>>> the array is in has a method that takes an array of string values.
>>>
>>> I want to construct an associative array such that the names in the
>>> first array are the keys to the values in the received array.
>>>
>>> this throws an error:
>>> --------------
>>>  def initialize
>>>     @labels = ['prov', 'area', 'zone', district', 'postalcode',
>>> 'city_prov', 'addr']
>>>     @pageData = {}
>>>   end
>>>
>>>   def adddata(data)
>>>     max = data.length
>>>     max -= 1
>>>     0.upto(max) {|i| @pageData[@labels[i]] => data[i] }
>>>   end
>>    def add_data(data)
>>      Hash[*@labels.zip(data).flatten]
>>    end
>>
>> Hash.[] takes an argument list with the even items being the keys and 
>> the odd items the values of the hash, i.e.
>>
>>    Hash[:a, 1, :b, 2, :c, 3]  => {:a => 1, :b => 2, :c => 3}
>>
>> The asterisk turns an array into an argument list, i.e.
>>
>>    foo(*[:a, :b, :c])
>>
>> is the same as
>>
>>    foo(:a, :b, :c)
>>
>> You can read about Array#zip and Array#flatten on the documentation 
>> pages, or by using ri from the terminal, e.g.
>>
>>    $ ri Array#zip
>>
>>
>> Cheers,
>> Daniel
> 
> The above works great if you're limited to the standard library.
> However, if you're allowed to use third party packages, I prefer hash
> slices for this sort of thing:
> 
> require 'hashslice'
> 
> def adddata(*data)
>    @pageData[*@labels] = *data
> end
> 
> IMHO this behavior should exist in the current Hash class. :)

I agree, and I'm using it myself. I just usually try to limit myself to 
the standard library when answering questions on this list, to minimize 
the hazzle the user has to go through.


Cheers,
Daniel