StackOverflow2013

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plurals

PO
primarykey
Id
9321772
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
1
CommunityOwnedDate
CreationDate
2012-02-17T01:39:30.610
FavoriteCount
0
LastActivityDate
2012-02-17T02:16:13.480
LastEditDate
2012-02-17T02:16:13.480
LastEditorUserId
1070504
OwnerUserId
1070504
ParentId
9321497
PostTypeId
2
Score
2
ViewCount
0
LastEditorDisplayName
text
Body
You can use a visitor pattern. but a visitor should know each of subtypes and define an action for it, so no default action, AFAIK <pre><code>class Visitor; class BaseMsg { //.. public: virtual void acceptVisitor(Visitor * v) = 0; }; class Msg1; class Msg2; class Visitor { // You can put here pure virtuals for sure every visitor will implement them public: virtual void action (Msg1 * msg) = 0; virtual void action (Msg2 * msg) = 0; }; class Msg1: public BaseMsg { //.. public: void acceptVisitor(Visitor * v){v->action(this);} }; class Msg2: public BaseMsg { //.. public: void acceptVisitor(Visitor * v){v->action(this);} }; class Visitor1 : public Visitor { // ... public: void action (Msg1 * msg) {/*...*/ cout << "I like the message!\n";} void action (Msg2 * msg) {/*...*/ cout << "I hate the message!\n";} // more messages and actions for them }; class Visitor2 : public Visitor{ // ... public: void action (Msg1 * msg) {/*...*/ cout << "Just fine\n";} void action (Msg2 * msg) {/*...*/ cout << "Sorry, I'm busy\n";} // more messages and actions for them }; int main() { BaseMsg * a = new Msg1; BaseMsg * b = new Msg2; Visitor * act = new Visitor1; Visitor * lazy = new Visitor2; // ............ // somewhere in a deep deep forest of your code a->acceptVisitor(act); b->acceptVisitor(act); // somewhere else a->acceptVisitor(lazy); b->acceptVisitor(lazy); delete act; delete lazy; delete a; delete b; return 0; } </code></pre> Output: <ul> <li>I like the message!</li> <li>I hate the message!</li> <li>Just fine</li> <li>Sorry, I'm busy</li> </ul>
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. PODesign pattern to avoid downcasting in message passing
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. USTim Kachko
UserOwnerUserId
1. USTim Kachko
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. This table or related slice is empty.
VotesPostIdCreationDate
1. This table or related slice is empty.
CommentsPostId
1. This table or related slice is empty.

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