How can we write a user defined method is Objective C / Swift with completion handler

Question

Please I will be helpful if you provide an example in either language. Thanks in Advance . .

Answer 1

Swift

func searchForStuff(_argument:String,completion: (data: [String]?) -> Void){

}

self.searchForStuff("aString") { (data) in

}

Objective c

- (void)searchForStuff:(NSString*)astring finishBlock:(void (^)(NSArray* data))finishBlock;

[self searchForStuff:@"aString" finishBlock:^(NSArray *data) {

}];