Page 267 - Asterisk™: The Future of Telephony

Because the database integration here becomes much more natural, Asterisk dialplans
becomes much more expressive as well. Below is a sample dialplan of a service provider
that imposes a time limit on outgoing calls using information from the database. To
remain simple:

# Let's assume we're offering VoIP service to customers
# whom we can identify with their callerid.
service {
# The line of code below performs an SQL SELECT
# statement on our database. The find_by_phone_number()
# method was created automatically because ActiveRecord
# found a phone_number column in the database. Adhearsion
# creates the "callerid" variable for us.
caller = Customer.find_by_phone_number callerid

usage = caller.usage_this_month
if usage >= 100.hours
play "sorry-cant-let-you-do-that"
else
play %w'to-hear-your-account-balance press-1
otherwise wait-moment'
choice = wait_for_digit 3.seconds
p choice
if choice == 1
charge = usage / 60.0 * caller.group.hourly_rate
play %W"your-account will-reflect-charge-of $#{charge}
this month for #{usage / 60} minutes and
#{usage % 60} seconds"
end
# We can also write back to the "usage_this_month"
# property of "caller". When the time method finishes,
# the database will be updated for this caller.
caller.usage_this_month += time do
# Code in this block is timed.
dial IAX/'main-trunk'/extension
end
caller.save
end
}
Robust database integration like this through Adhearsion brings new ease to developing
for and managing a PBX. Centrally persistent information allows Asterisk to integrate
with other services cleanly while empowering more valuable services whose needs are
beyond that of traditional Asterisk development technologies.

Distributing and reusing code
Because an Adhearsion application resides within a single folder, completely copying
the VoIP application is as simple as zipping the files. For one of the first times in the
Asterisk community, users can easily exchange and build upon one another’s successful

Asterisk Development with Adhearsion | 239