# breakpoint(receiveSubscription:receiveOutput:receiveCompletion:) Raises a debugger signal when a provided closure needs to stop the process in the debugger. ``` func breakpoint(receiveSubscription: ((any Subscription) -> Bool)? = nil, receiveOutput: ((Self.Output) -> Bool)? = nil, receiveCompletion: ((Subscribers.Completion) -> Bool)? = nil) -> Publishers.Breakpoint ``` ## Parameters `receiveSubscription` A closure that executes when the publisher receives a subscription. Return `true` from this closure to raise `SIGTRAP`, or false to continue. `receiveOutput` A closure that executes when the publisher receives a value. Return `true` from this closure to raise `SIGTRAP`, or false to continue. `receiveCompletion` A closure that executes when the publisher receives a completion. Return `true` from this closure to raise `SIGTRAP`, or false to continue. ## Return Value A publisher that raises a debugger signal when one of the provided closures returns `true`. ## Discussion Use [`breakpoint(receiveSubscription:receiveOutput:receiveCompletion:)`](/documentation/Combine/Publisher/breakpoint(receiveSubscription:receiveOutput:receiveCompletion:)) to examine one or more stages of the subscribe/publish/completion process and stop in the debugger, based on conditions you specify. When any of the provided closures returns `true`, this operator raises the `SIGTRAP` signal to stop the process in the debugger. Otherwise, this publisher passes through values and completions as-is. In the example below, a [`PassthroughSubject`](/documentation/Combine/PassthroughSubject) publishes strings to a breakpoint republisher. When the breakpoint receives the string “`DEBUGGER`”, it returns `true`, which stops the app in the debugger. ``` let publisher = PassthroughSubject() cancellable = publisher .breakpoint( receiveOutput: { value in return value == "DEBUGGER" } ) .sink { print("\(String(describing: $0))" , terminator: " ") } publisher.send("DEBUGGER") // Prints: "error: Execution was interrupted, reason: signal SIGTRAP." // Depending on your specific environment, the console messages may // also include stack trace information, which is not shown here. ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)