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Add onChange() method to V3 Trigger #9359

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Add onChange() method to V3 Trigger #9359

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13 changes: 13 additions & 0 deletions commandsv3/src/main/java/org/wpilib/command3/Trigger.java
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,19 @@ public Trigger(Scheduler scheduler, EventLoop loop, BooleanSupplier condition) {
m_loop.bind(m_eventLoopCallback);
}

/**
* Starts the command when the condition changes.
*
* @param command the command to start
* @return this trigger, so calls can be chained
*/
Comment on lines +118 to +123
public Trigger onChange(Command command) {
requireNonNullParam(command, "command", "onChange");
addBinding(BindingType.SCHEDULE_ON_RISING_EDGE, command);
addBinding(BindingType.SCHEDULE_ON_FALLING_EDGE, command);
Comment on lines +126 to +127

@chatgpt-codex-connector chatgpt-codex-connector Bot Aug 28, 2026

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P2 Badge Skip the initial sample in onChange

Because m_previousSignal is null until the trigger is first polled, poll() classifies the initial sample as either a rising or falling edge. Registering the command for both edge types therefore guarantees that onChange() schedules it on the first Scheduler.run() even when the supplier has never changed, contrary to the method contract and the existing V2 onChange() behavior. This needs a dedicated binding or baseline handling that ignores the initial sample.

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return this;
}
Comment on lines +124 to +129

/**
* Starts the given command whenever the condition changes from `false` to `true`.
*
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