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  1. Qt
  2. QTBUG-102741

Qt::UniqueConnection should be the default type of connection

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    Details

    • Type: Suggestion
    • Status: Open
    • Priority: P4: Low
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: Core: Object Model
    • Labels:
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      Description

      I believe that Qt::UniqueConnection should be the default type of connection. Ideally, it should assert in DEBUG if a connection is not unique.

      The reason is that during more than 10 years of using Qt, I have not yet seen any single use case where multiple connection between one pair of signal and slot would be desirable. On the other hand I have already seen many examples where wrong code resulted in multiplying connections (kind of "connection leakage") which caused bad performance and sometimes a very hard-to-catch errors. Therefore it is crucial to catch these errors as soon as possible.

      So I think that unique connection should be the default and should be asserted in DEBUG. Multiple connections should be allowed, but only via the optional flag, e.g. something like Qt::MultiConnection.

      I believe that enforcing unique connection by default should be possible for signal -> slot connection. I am not sure though if this is possible for signal -> lambda or signal -> free function connections... Maybe experts could tell.

      I know this is a breaking change, possible only when code compatibility is not strictly kept, maybe when transitioning from Qt6 to Qt7.

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            Assignee:
            thiago Thiago Macieira
            Reporter:
            vladimir.kraus Vladimir Kraus
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              Updated:

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