Following DRY is practised religously in my current project. Recently, I identified a case where code repetition had long been ignored. We used to pass either a domain object or a command object in the view model. Due to this, many domain methods had to be duplicated in the command object. This was probablematic because one would easily forget to create\/modify a function in the command object if it was created\/modified in the domain object. The code was smelling bad. The classes were something like this:
\n[java]
\nClass College{
\n\/\/attributes<\/p>\n
\/\/somethods
\n}<\/p>\n
Class CollegeCO{
\nCollege college<\/p>\n
\/\/other attributes and constraints<\/p>\n
\/\/ repetitive College methods<\/p>\n
}
\n[\/java]<\/p>\n
Groovy intercepts all methods and property access via invokeMethod and get\/SetProperty property hooks. So all I needed to do was to override invokeMethod() and propertyMissing() functions in the CommandObject like this:<\/p>\n
[java]
\ndef invokeMethod(String name, args) {
\n college.invokeMethod(name, args)
\n }<\/p>\n
def propertyMissing(String name) {
\n college."$name"
\n }
\n[\/java]<\/p>\n
So any missing method or property call on command object was automatically delegated to the college object. This is a simple way of utilising the Delegation Patttern using Groovy.<\/p>\n
Hope this helps.<\/p>\n
Imran Mir
\nImran[at]intelligrape.com<\/p>\n","protected":false},"excerpt":{"rendered":"
Following DRY is practised religously in my current project. Recently, I identified a case where code repetition had long been ignored. We used to pass either a domain object or a command object in the view model. Due to this, many domain methods had to be duplicated in the command object. This was probablematic because […]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":7,"footnotes":""},"categories":[7],"tags":[1017,1015,1016],"class_list":["post-8042","post","type-post","status-publish","format-standard","hentry","category-grails","tag-delegation-pattern","tag-invokemethod","tag-propertymissing"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t