A delegate is a reference to a method. Whereas objects can easily be sent as parameters into methods, constructor or whatever, methods are a bit more tricky. But every once in a while you might feel the need to send a method as a parameter to another method, and that’s when you’ll need delegates. using … Read more
You need to declare the type of the protocol as AnyObject. protocol ProtocolNameDelegate: AnyObject { // Protocol stuff goes here } class SomeClass { weak var delegate: ProtocolNameDelegate? } Using AnyObject you say that only classes can conform to this protocol, whereas structs or enums can’t.
An Objective-C delegate is an object that has been assigned to the delegate property another object. To create one, you define a class that implements the delegate methods you’re interested in, and mark that class as implementing the delegate protocol. For example, suppose you have a UIWebView. If you’d like to implement its delegate’s webViewDidStartLoad: … Read more
The difference between Func and Action is simply whether you want the delegate to return a value (use Func) or not (use Action). Func is probably most commonly used in LINQ – for example in projections: list.Select(x => x.SomeProperty) or filtering: list.Where(x => x.SomeValue == someOtherValue) or key selection: list.Join(otherList, x => x.FirstKey, y => … Read more
You can use the Func delegate in .net 3.5 as the parameter in your RunTheMethod method. The Func delegate allows you to specify a method that takes a number of parameters of a specific type and returns a single argument of a specific type. Here is an example that should work: public class Class1 { … Read more
When you want to treat lambda expressions as expression trees and look inside them instead of executing them. For example, LINQ to SQL gets the expression and converts it to the equivalent SQL statement and submits it to server (rather than executing the lambda). Conceptually, Expression<Func<T>> is completely different from Func<T>. Func<T> denotes a delegate … Read more