How to create optional methods in a protocol

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If a protocol method is marked as optional, you can check whether an object implements that method before attempting to call it.
As an example, the contact chart view might test for the segment title method like this:
NSString *contactTitle;
if ([self.dataSource respondsToSelector:@selector(titleForContactAtIndex:)]) {
contactTitle = [self.dataSource titleForContactAtIndex:index];
}
The respondsToSelector: method uses a selector, which refers to the identifier for a method after compilation. You can provide the correct identifier by using the @selector() directive and specifying the name of the method.
If the data source in this example implements the method, the title is used; otherwise, the title remains nil.

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How to create optional methods in a protocol

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