First make your file delegate for UITextField @interface MYLoginViewController () <UITextFieldDelegate> @end Then add this method to your code. – (BOOL)textFieldShouldReturn:(UITextField *)textField { [textField resignFirstResponder]; return YES; } Also add self.textField.delegate = self;
I like to think of a delegate as “a pointer to a function”. This goes back to C days, but the idea still holds. The idea is that you need to be able to invoke a piece of code, but that piece of code you’re going to invoke isn’t known until runtime. So you use … Read more
The Java idiom for function-pointer-like functionality is an an anonymous class implementing an interface, e.g. Collections.sort(list, new Comparator<MyClass>(){ public int compare(MyClass a, MyClass b) { // compare objects } }); Update: the above is necessary in Java versions prior to Java 8. Now we have much nicer alternatives, namely lambdas: list.sort((a, b) -> a.isGreaterThan(b)); and … Read more
These are good questions, and its great to see that you’re doing this research and seem concerned with learning how to “do it right” instead of just hacking it together. First, I agree with the previous answers which focus on the importance of putting data in model objects when appropriate (per the MVC design pattern). … Read more
The reason that you avoid retaining delegates is that you need to avoid a retain cycle: A creates B A sets itself as B’s delegate … A is released by its owner If B had retained A, A wouldn’t be released, as B owns A, thus A’s dealloc would never get called, causing both A … Read more
You have an incredible number of choices to achieve delegates in C++. Here are the ones that came to my mind. Option 1 : functors: A function object may be created by implementing operator() struct Functor { // Normal class/struct members int operator()(double d) // Arbitrary return types and parameter list { return (int) d … Read more
Short answer : no. Longer answer that may not be relevant: If you assign the lambda to a delegate type (such as Func or Action) you’ll get an anonymous delegate. If you assign the lambda to an Expression type, you’ll get an expression tree instead of a anonymous delegate. The expression tree can then be … Read more
Not really, no. You may be able to achieve the same effect by using reflection to get Method objects you can then invoke, and the other way is to create an interface with a single ‘invoke’ or ‘execute’ method, and then instantiate them to call the method your interested in (i.e. using an anonymous inner … Read more
Action myDelegate = delegate(){Console.WriteLine(“I did it!”);}; MyEvent += myDelegate; // …. later MyEvent -= myDelegate; Just keep a reference to the delegate around.
An Event declaration adds a layer of abstraction and protection on the delegate instance. This protection prevents clients of the delegate from resetting the delegate and its invocation list and only allows adding or removing targets from the invocation list.