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Chain-of-responsibility pattern in Ruby
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module PurchasePower | |
BASE = 500 | |
private | |
attr_accessor :successor | |
end | |
class Manager | |
include PurchasePower | |
ALLOWABLE = 10 * BASE | |
def process_request(request) | |
if request.amount < ALLOWABLE | |
puts("Manager will approve $#{request.amount}") | |
return | |
elsif !successor.nil? | |
successor.process_request(request) | |
end | |
end | |
end | |
class Director | |
include PurchasePower | |
ALLOWABLE = 20 * BASE | |
def process_request(request) | |
if request.amount < ALLOWABLE | |
puts("Director will approve $#{request.amount}") | |
return | |
elsif !successor.nil? | |
successor.process_request(request) | |
end | |
end | |
end | |
class VicePresident | |
include PurchasePower | |
ALLOWABLE = 40 * BASE | |
def process_request(request) | |
if request.amount < ALLOWABLE | |
puts("VicePresident will approve $#{request.amount}") | |
return | |
elsif !successor.nil? | |
successor.process_request(request) | |
end | |
end | |
end | |
class President | |
include PurchasePower | |
ALLOWABLE = 60 * BASE | |
def process_request(request) | |
if request.amount < ALLOWABLE | |
puts("President will approve $#{request.amount}") | |
return | |
else | |
puts "Your request for $#{request.amount} needs a board meeting!" | |
end | |
end | |
end | |
class PurchaseRequest | |
def initialize(number, amount, purpose) | |
@number = number | |
@amount = amount | |
@purpose = purpose | |
end | |
def amount | |
@amount | |
end | |
end | |
class Approvers | |
def initialize(*approvers) | |
@approvers = approvers.map(&:new) | |
end | |
def add_approver(approver) | |
@approvers << approver | |
end | |
def delete_approver(approver) | |
@approvers.delete(approver) | |
end | |
def approvers_list | |
@approvers | |
end | |
end | |
class CheckAuthority | |
def initialize(approvers) | |
@approvers = approvers | |
@starting_approver = build_chains.first | |
end | |
def checking | |
loop do | |
$stdout.flush | |
puts "Enter the amount to check who should approve your expenditure." | |
puts ">>" | |
@starting_approver.process_request PurchaseRequest.new(0, gets.to_i, 'General') | |
end | |
end | |
private | |
def build_chains | |
@approvers.each_cons(2).map { |prev_approver, next_approver| prev_approver.send :successor=, next_approver } | |
end | |
end | |
approvers = Approvers.new(Manager, Director, VicePresident, President) | |
CheckAuthority.new(approvers.approvers_list).checking |
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Arup-iMac:arup_ruby shreyas$ ruby a.rb | |
Enter the amount to check who should approve your expenditure. | |
>> | |
1200 | |
Director will approve $1200 | |
Enter the amount to check who should approve your expenditure. | |
>> | |
2000 | |
Director will approve $2000 | |
Enter the amount to check who should approve your expenditure. | |
>> | |
^[[A^[[B | |
Director will approve $0 | |
Enter the amount to check who should approve your expenditure. | |
>> | |
3000 | |
Director will approve $3000 | |
Enter the amount to check who should approve your expenditure. | |
>> | |
40000 | |
Your request for $40000 needs a board meeting! | |
Enter the amount to check who should approve your expenditure. | |
>> | |
4000 | |
Director will approve $4000 | |
Enter the amount to check who should approve your expenditure. | |
>> | |
30000 | |
Your request for $30000 needs a board meeting! | |
Enter the amount to check who should approve your expenditure. | |
>> | |
10000 | |
VicePresident will approve $10000 | |
Enter the amount to check who should approve your expenditure. | |
>> |
Author
aruprakshit
commented
Feb 18, 2015
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