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How to create optional methods in a protocol

Tarun Kumar143726-Sep-2015

I noticed that in creating protocols we can define methods as optional in the iPhone SDK, for example UIActionSheetDelegate protocol.

How can I define a protocol of my own, and set as optional of few of the methods?

iphoneiphone ios objective c 
Updated on 27-Sep-2015
Tarun Kumar

Tarun Kumar

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Anonymous User

Anonymous User

27-Sep-2015
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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