Chain-of-responsibility: "Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it."
package require snit
snit::type handler {
option -handleIf
variable condition false
onconfigure -handleIf value {set condition $value}
option -handleBy
variable consequent {}
onconfigure -handleBy value {set consequent $value}
option -elseReportTo
variable alternative {}
onconfigure -elseReportTo value {
set alternative [concat $value handle \$request]
}
method handle request {
if $condition $consequent $alternative
}
}Example:
proc main args {
handler Tom -handleIf {
$request >= 0 && $request < 10
} -handleBy {
puts "$self handled request $request"
} -elseReportTo Gus
handler Gus -handleIf {
$request >= 10 && $request < 20
} -handleBy {
puts "$self handled request $request"
} -elseReportTo Mary
handler Mary -handleIf {
$request >= 20 && $request < 30
} -handleBy {
puts "$self handled request $request"
}
foreach request [list 2 5 14 22 18 38 3 27 20] {
Tom handle $request
}
}