Before calling an optional protocol method, it is good to check if the delegate has implemented the methods. This is usually done using the following pattern: if (_delegate && [_delegate.respondsToSelector:@selector(method1)]) { // Do your thing } Turns out that some days ago, I faced a better way to do this kind of check by creating a struct an…

TestClass.h

// TestClass.h
#import <Foundation/Foundation.h>
@protocol TestProtocol <NSObject>
@optional
- (void) testProtocolMethod;
@end

@interface TestClass: NSObject
{
    // Struct that will hold the methods that the delegate implements
    struct {
        unsigned int respondsToTestProtocolMethod: 1;
    } _delegateFlags;
}

@property (nonatomic, weak) id<TestProtocol> delegate;

- (id)init;
- (void)doSomething;


// TestClass.m
#import "TestClass.h"

@implementation TestClass

@synthesize delegate=_delegate;

// Init methods...

- (void)setDelegate:(id<TestProtocol>)delegate
{
    // Sets the delegate and populates the flags struct
    _delegate = delegate;
    _delegateFlags.respondsToTestProtocolMethod = [_delegate respondsToSelector:@selector(testProtocolMethod)];
}

- (void)doSomething
{
    // We can check only the flag instead of calling respondsToSelector
    (if _delegateFlags.respondsToTestProtocolMethod) {
        // Do your thing and be happy
    }
}
@end