StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POUsing a mixin (?) to make stream i/o easier
primarykey
Id
7742337
data
AcceptedAnswerId
0
AnswerCount
1
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2011-10-12T15:16:11.690
FavoriteCount
0
LastActivityDate
2011-10-12T15:43:20.257
LastEditDate
2011-10-12T15:36:59.450
LastEditorUserId
484230
OwnerUserId
484230
ParentId
0
PostTypeId
1
Score
3
ViewCount
118
LastEditorDisplayName
text
Body
Since many students I work with on common code have some problems comprehending proper stream operator overloading, I tried to create a helper template (don't know if this is a real mixin) to facilitate the code and insure correct operator implementation. Here it comes: <pre><code>template<typename T> struct IoEnabled { friend std::ostream& operator<<(std::ostream& out, T const& val) { return val.print(out); } friend std::istream& operator>>(std::istream& in, T& val) { return val.scan(in); } friend QTextStream& operator<<(QTextStream& out, T const& val) { return val.print(out); } friend QTextStream& operator>>(QTextStream& in, T& val) { return val.scan(in); } friend QDebug operator<<(QDebug dbg,T const& val){ std::stringstream myStream; myStream << val; dbg.nospace() << myStream.str().c_str(); return dbg; } }; </code></pre> Inheriting class: <pre><code>class Foo: private IoEnabled<Foo> { protected: int mData; public: template<typename U> U& scan(U& in) { in >> mData; return in; } template<typename U> U& print(U& out) const { out << mData; return out; } } </code></pre> The downsides of this implementation as far as I see them at the moment: <ul> <li>Does not work for 3rd party types</li> <li>Includes inheritance and thus tight coupling with the IoClass although not every user might need Io for a certain type</li> </ul> The ups: <ul> <li>It works ;-)</li> <li>Similar stream classes can be added without modifying all classes and withou writing specific new code for every class</li> </ul> Since I'm not very experienced in the usage of mixins and tend to violate coding guidelines once in a while, I'd like to know if this is an appropriate usage of a mixin or how one could obtain a similar effect with another more suitable technique. Many Thanks, Martin
Tags
<c++><templates><generics><mixins><crtp>
Title
Using a mixin (?) to make stream i/o easier
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USMartin
UserOwnerUserId
1. USMartin
plurals
PostLinksPostIdRelatedPostId
1. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. VO
 singulars
 PostPostId
 POUsing a mixin (?) to make stream i/o easier
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
2. VO
 singulars
 PostPostId
 POUsing a mixin (?) to make stream i/o easier
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
3. VO
 singulars
 PostPostId
 POUsing a mixin (?) to make stream i/o easier
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
CommentsPostId
1. This table or related slice is empty.

Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.