On Sun, Nov 4, 2012 at 6:02 AM, Abram <[email protected]> wrote:
> Basically it just chains on to the previous db query, but still runs a new
> one.. it doesn't query the active record relation object. Also, you cannot
> query an array of objects.. say @products = Product.all ... then say
> @products.where(:color=>"black") .. You will get NoMethodError: undefined
> method `where' for #<Array:0x00000003918108>
If you're running the code in the console, it hits the db immediately. But
if it's in the actual application, it won't hit the db until you need to
access the records
which usually happens when you call each or map or collect on the active
relation object. So given your code, if you want to get all black and
small objects, you can
@products = Product.where(color: 'black')
@products = @products.where(size: 'small')
these two lines will not actually create the product records and will not
yet hit the db until you want to iterate each of the products.
As for calling Product.all, I checked the api and it doesn't explicitly say
that #all returns an array. But if you know that beforehand, you shouldn't
have any issues
with chaining methods.
>
>
> On Sunday, November 4, 2012 11:00:29 AM UTC+13, Abram wrote:
>>
>> Well, it does, but it hits the DB again.
>>
>> On Sunday, November 4, 2012 10:43:29 AM UTC+13, Abram wrote:
>>>
>>> When I began learning rails I found it frustrating that array and active
>>> record relation objects could not be queried in the same fashion as
>>> database tables. Before too much confusion let me explain.
>>>
>>>
>>> When I want something from a database table I simply write something
>>> like: Product.where(:color=>'black') NOW, if I put a .to_sql after that
>>> statement I see something like "SELECT \"styles\".* FROM \"styles\" WHERE
>>> \"styles\".\"color\" = 'black'"
>>>
>>>
>>> So clearly, rails is magically converting that friendly statement into
>>> something more meaningful to the backend. That's fantastic and makes my
>>> life wonderful.
>>>
>>>
>>> So here's my problem.. after running the query I am returned an active
>>> record relation, which let's say is called @products. Now, let's say I want
>>> to further break that list of products into products that are big and
>>> small. This would require one of two things.. either I must hit the
>>> database twice being more selective, or I must iterate over @products using
>>> a block and such ruby magic as collect/map/select/etc...
>>>
>>>
>>> To me neither of the above is a great option, and I must admit while
>>> learning ruby on rails this was one of the biggest stumbling blocks for me,
>>> and one that has produced a massive amount of stackoverflow headaches for
>>> many others.
>>>
>>>
>>> My suggestion to rails developers is to make rails more accessible to
>>> beginners by allowing programmers to apply the same simplicity of writing
>>> an active record query to querying an active record relation object or
>>> array of model objects.
>>>
>>>
>>> For example, I want to now take @products and say:
>>>
>>>
>>> @products.where(:size=>"small"**) and have this converted automagically
>>> by rails to the appropriate statement @products.select{|product|
>>> product.size == 'small'}
>>>
>>>
>>> I suppose this could work if rails were to query the object type first
>>> before performing the query. Is the object type an array or active record
>>> relation, and is it in the expected format (collection of appropriate
>>> objects)? If it is, then treat it as a virtual table and instead of
>>> performing an sql query, hit it with a select block, etc.
>>>
>>>
>>> I know understanding the underlying ruby code is good, and at times
>>> would be preferable to using active record style commands.. but for new
>>> users getting off the ground, I think having both options would be
>>> beneficial. Also, I feel it would be more consistency to the framework
>>> generally.
>>>
>>>
>>> I have also posted this at reddit http://www.reddit.com/**
>>> r/rails/comments/12kyho/**suggestion_for_rails_4_what_**
>>> are_pros_and_cons/<http://www.reddit.com/r/rails/comments/12kyho/suggestion_for_rails_4_what_are_pros_and_cons/>
>>>
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