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name: webrtc/sdk/objc-group-optional-protocol-methods-at-bottom description: When declaring Objective-C delegate protocols, place new callbacks under @optional for backward compatibility and group all @optional methods at the bottom rubric: readability severity: should_fix

Rule. In Objective-C protocol declarations (such as delegate or observer protocols), group all @optional methods together in a single @optional section at the bottom of the protocol instead of interleaving @optional and @required directives. Additionally, when adding new callback methods to existing public protocols, declare them as @optional to maintain backward compatibility for existing conforming implementations.

Why. In Objective-C protocols, methods are @required by default. Grouping @optional methods at the bottom avoids repetitive directive switching and keeps the required interface contract distinct. Placing new delegate callbacks under @optional ensures existing downstream implementations continue to compile and work without breaking changes.

Examples

Bad:

@protocol RTCPeerConnectionDelegate <NSObject>
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didChangeIceConnectionState:(RTCIceConnectionState)newState;

// Bad: New callback added as required, breaking existing downstream implementors.
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didChangeIceGatheringState:(RTCIceGatheringState)newState;

// Bad: Interleaving @optional and @required directives.
@optional
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didChangeConnectionState:(RTCPeerConnectionState)newState;

@required
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didGenerateIceCandidate:(RTCIceCandidate *)candidate;
@end

Good:

@protocol RTCPeerConnectionDelegate <NSObject>
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didChangeIceConnectionState:(RTCIceConnectionState)newState;
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didGenerateIceCandidate:(RTCIceCandidate *)candidate;

@optional
// All optional and newly added callbacks grouped together at the bottom.
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didChangeConnectionState:(RTCPeerConnectionState)newState;
- (void)peerConnection:(RTCPeerConnection *)peerConnection
    didChangeIceGatheringState:(RTCIceGatheringState)newState;
@end