If the application invokes handler.nack() or allows handler to go out of scope, then the service will redeliver the message.
With exactly-once delivery subscriptions, the service will stop redelivering the message once the application invokes handler.ack() and the invocation succeeds. With best-efforts subscriptions, the service may redeliver the message, even after a successful handler.ack() invocation.
If handler is not an rvalue, you may need to use std::move(handler).ack() or std::move(handler).nack().
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eVersion 2.37.0-rc is the latest release candidate for the C++ Pub/Sub library, with version 2.36.0 being the current stable release.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation provides versioned references for \u003ccode\u003ePullResponse\u003c/code\u003e across multiple releases, spanning from 2.11.0 to the current release candidate, 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003ePullResponse\u003c/code\u003e is associated with handling the acknowledgment or negative acknowledgment of messages, and the service will redeliver messages if \u003ccode\u003ehandler.nack()\u003c/code\u003e is called or the handler goes out of scope.\u003c/p\u003e\n"],["\u003cp\u003eThe behavior of message redelivery after acknowledgment depends on the subscription type, where exactly-once delivery subscriptions will stop redelivering after a successful \u003ccode\u003ehandler.ack()\u003c/code\u003e, while best-effort subscriptions may still redeliver.\u003c/p\u003e\n"],["\u003cp\u003eUsing \u003ccode\u003estd::move()\u003c/code\u003e on the handler may be required for calling ack() or nack() if the handler is not an rvalue.\u003c/p\u003e\n"]]],[],null,[]]
