Re: Compare and sort one array according to another.

On Mon, Jun 17, 2013 at 10:39 PM, Jes=FAs Gabriel y Gal=E1n
<[e-mail]> wrote:
> On Mon, Jun 17, 2013 at 9:56 PM, masta Blasta <[e-mail]> wrot=
e:
>> Joel Pearson wrote in post #1112686:
>>> masta Blasta wrote in post #1112677:
>>>> Joel Pearson wrote in post #1112665:
>>>>> If the items within each array belong to each other, how about a
>>>>> multidimensional array?
>>>>>
>>>>> arr =3D [
>>>>> [ Obj1(prop1, prop2, id), OthrObj1(prop1, prop2, ref_id) ],
>>>>> [ Obj2(prop1, prop2, id), OthrObj2(prop1, prop2, ref_id) ],
>>>>> [ Obj3(prop1, prop2, id), OthrObj3(prop1, prop2, ref_id) ]
>>>>> ]
>>>>>
>>>>>
>>>>> All the sorting is dealt with together then:
>>>>>
>>>>> sorted_arr =3D arr.sort_by { |obj1, obj2| obj1.id }
>>>>
>>>> I don't quite understand everything that's happening here. Can you
>>>> elaborate a bit more on your solution.
>>>
>>> I'm going by your comment here:
>>> "The objects in arr2 have a 1-1 relationship with the objects in arr1"
>>>
>>> If the objects are interlinked, rather than trying to keep two separate
>>> arrays and sorting them side-by-side (which can easily go wrong), you
>>> could simply connect the pairs into their own arrays all inside another
>>> array.
>>>
>>> This has the benefit that once you put the pair into their own array,
>>> they are connected without you having to worry about having to do
>>> everything the same with array1 and array2.
>>>
>>> Then you can iterate through the large array like this:
>>>
>>> arr.each { |subarray| some_method( subarray[0], subarray[1] ) }
>>>
>>> In this example you can access each of the smaller arrays inside your
>>> array. [0] is each object and [1] is each otherobject
>>>
>>> Or like this:
>>>
>>> arr.each { |object, otherobject| some_method( object, otherobject ) }
>>>
>>> This example is functionally the same as the previous one, but you're
>>> using parallel assignment to place each object from the array into its
>>> own variable so it's easier to read.
>>>
>>> Using this approach, you can sort the larger array containing objects
>>> and otherobjects by whatever criteria you want, and they'll stay
>>> together as a pair within the larger array.
>>>
>>> This will sort each array within the parent by the first object's id:
>>>
>>> arr =3D arr.sort_by { |object, otherobject| object.id }
>>>
>>> This does the same thing, but with the second object's id:
>>>
>>> arr =3D arr.sort_by { |object, otherobject| otherobject.id }
>>>
>>> The best way to grasp how this is works is to do it in IRB and play
>>> around with the results.
>>
>> I just learned something new about ordering arrays! However this doesn't
>> actually solve the original problem. Your solution expects both arrays
>> to be properly sorted, and then keeps them together if one or the other
>> is re-ordered.
>>
>> Originally only one of the arrays was properly sorted, and the other had
>> then to be ordered to match.
>>
>> Here is some better sample data:
>> terms =3D [
>>     {:id=3D>3, :name=3D>"term1", :version=3D>2},
>>     {:id=3D>4, :name=3D>"term2", :version=3D>2},
>>     {:id=3D>8, :name=3D>"term3", :version=3D>1}
>> ]
>>
>> arr2 =3D [
>>     {:term_id=3D>4, :name=3D>"assoc1"},
>>     {:term_id=3D>8, :name=3D>"assoc2"},
>>     {:term_id=3D>3, :name=3D>"assoc3"}
>> ]
>>
>> so 'terms' is properly sorted, and now we want arr2 to follow that
>> order. So after our operation arr2 should look like:
>>
>> arr2 =3D [
>>     {:term_id=3D>3, :name=3D>"assoc3"},
>>     {:term_id=3D>4, :name=3D>"assoc1"},
>>     {:term_id=3D>8, :name=3D>"assoc2"}
>>
>> ]
>>
>> These are ActiveRecord objects. A SQL solution is possible but the query
>> is painfully long due to complex associations. Since the arrays are
>> usually small 3-5 records, i was hoping i could just sort them
>> programmatically.
>
> Did you try Robert Klemme's solution? Translated to this new example:
>

Typo: that should have been

> arr2.sort_by {|o| terms.find_index {|a| o[:term_id] =3D=3D a[:id]}}
>
> =3D> [{:term_id=3D>3, :name=3D>"assoc3"}, {:term_id=3D>4, :name=3D>"assoc=
1"},
> {:term_id=3D>8, :name=3D>"assoc2"}]
>
> Jesus.