Ludzie pragną czasami się rozstawać, żeby móc tęsknić, czekać i cieszyć się z powrotem.
Even within a single prod-
zon product catalog, as they provide ev-
the performance of your application, so
uct category, some products will have
ery product in the catalog with a unique
it is used by default if you do not speci-
properties that others are missing. Some
identifier. For a book, the ASIN is the same
fy a preference.
properties, however, such as the price, are
as the ISBN number, but for other items,
You can make life easier for yourself by
logically common to all products; every-
it’s an arbitrary alphanumeric string con-
specifying your usual requirements for
thing has a price at Amazon. At this writ-
cocted by Amazon. Many of the AWS API
new Request objects in a configuration
ing, Listing One yields the results in Fig-
calls deal directly with ASINs to unique-
file, to be found at either /etc/amazonrc
ure 1. Rather than use the iterator block
ly identify the product in question, so
or ~/.amazonrc. For example:
form of the search, this would also have
you’ll likely find yourself passing them
dev_token = 'D23XFCO2UKJY82'
worked as well:
around a lot.
associate = 'calibanorg-20'
If you didn’t elect to use caching at the
response = r.keyword_search
cache_dir = '/tmp/amazon/cache'
('ruby programming', 'books')
time of request object instantiation, you
locale = 'de'
can elect to do so now by establishing a
Using this approach, response now con-
cache object for future searches. The cache
Now, any Request objects you create in-
tains the literal REST response returned
directory given is created, if it does not
herit these characteristics. They can still be
by AWS; you can print or puts it and see.
already exist.
manually overridden as required, however.
This is sometimes useful for the purpose
The underlying concept of Listing One
r.cache = Cache.new( '/tmp/amazon' )
of debugging. You can still iterate over
can be inverted to produce a program that
notifies you whenever a new album by
your favorite artist appears in the Amazon
Programming Ruby: The Pragmatic Programmers' Guide by Dave Thomas, Chad Fowler, Andy Hunt (ASIN 0974514055) for $44.95
catalogue for preorder. This works by
Not yet released.
looking for products whose availability
contains the string “not yet released.” In
Ruby Developer's Guide by Michael Neumann, Lyle Johnson, Robert Feldt, Listing Two, the “favourites” array con-Lyle Johnson, Jonothon Ortiz (ASIN 1928994644) for $32.97
Usually ships in 11 to 12 days
tains tuples of product names and catalog
sections. The program then searches the
Sams Teach Yourself Ruby in 21 Days by Mark Slagell (ASIN 0672322528) relevant parts of the UK catalogue for
for $28.39
matching products that have not yet been
Usually ships in 1 to 3 weeks
released. It may be useful to mail the out-
Ruby In A Nutshell by Yukihiro Matsumoto (ASIN 0596002149) for $16.47
put of this program to yourself on a week-
Usually ships in 24 hours
ly basis. When run, the output looks like
Figure 2.
The Ruby Way by Hal Fulton (ASIN 0672320835) for $27.19
Usually ships in 24 hours
As a final demonstration of the useful-
ness of this kind of monitoring, I present
Making Use of Ruby by Suresh Mahadevan, Suresh Mahadevan, Rashi Gupta, a program that is designed to be run au-Shweta Bhasin, Madhushree Ganguly, Ashok Appu (ASIN 047121972X) for $23.80
tomatically on a daily basis. It tracks the
Usually ships in 24 hours
price of an item in the “electronics” sec-
Game Programming with Python, Lua, and Ruby by Tom Gutschmidt (ASIN
tion of the catalog and produces output
1592000770) for $26.39
whenever the price changes.
Usually ships in 24 hours
Items in Amazon’s catalog can under-
go quite a lot of price fluctuation within
Figure 1: Output from Listing One.
a relatively short period of time. Some-
times, the price of an expensive item drops
Bullet CD by Trafik
$50.00 or more, only to rise again mere
(ASIN B0002NRMMY)
hours later. I don’t know why this hap-
pens, but knowing that it does and hav-
Only Fools And Horses - Sleepless In Peckham DVD
(ASIN B0002PC39Y)
ing AWS at your disposal lets you take ad-
vantage of these fluctuations to buy at a
Only Fools And Horses - The Complete Series 1 To 7 DVD
favorable moment.
(ASIN B0002XOZSS)
Have a look at Listing Three. Replace
Only Fools And Horses - Christmas Specials DVD
the ASIN with that of a product in which
(ASIN B0002XOZV0)
you’re interested and run the program
once an hour or so, perhaps from cron.
The Office: Christmas Specials [2003] DVD
There are many kinds of searches that
(ASIN B0001WHUFK)
can be performed via AWS. You’ve already
The Office: Complete Box Set (Series 1 - 2 plus Christmas Specials) [2001] DVD
seen #keyword_search and #asin_search
(ASIN B0002IAQFY)
in the example programs, but there are
other common search types, such as #ac-
Figure 2: Output from Listing Two.