From: Jamey Cribbs <cribbsj@...>
Date: 2006-07-22T04:44:19+09:00
Subject: Re: [ANN] Mongoose 0.2.0

John W. Long wrote:
> Jamey Cribbs wrote:
>> Plane.find do |plane|
>>    plane.speed > 350
>>    plane.any do
>>        plane.country == 'USA'         plane.country == 'Great Britain'
>>    end
>> end
>>
>> Now, looks like this:
>>
>> Plane.find do
>>    speed > 350
>>    any do
>>        country == 'USA'
>>        country == 'Great Britain'
>>    end
>> end
>
> James, could you elaborate on how this is done? I would assume that 
> the first method is better because you don't lose the the surrounding 
> scope. What's going on in that do block?
Actually, I like the second way better, because you don't have to 
clutter up your query with lots of references to your table class.

The way it works is that in the Plane.find method, I grab the block and 
pass it to #instance_eval.  This executes the block in the Plane classes 
environment, so it knows that when it sees the attribute "speed" or 
"country" in the block, it knows to call Plane.speed and Plane.country.  
Planes.speed happens to be a reference to a SkiplistColumn instance and 
it knows how to handle the "> 350" passed to it.

I have to credit Ezra for pointing me to this.

The reference to "any" just calls Plane.any which is a method in the 
Plane class that knows how to take the block inside of it and format it 
as a sub-query of the main query.

Jamey

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