Yes. Func<> returns the type specified as the final generic type parameter, such that Func<int> returns an int and Func<int, string> accepts an integer and returns a string. Examples: Func<int> getOne = () => 1; Func<int, string> convertIntToString = i => i.ToString(); Action<string> printToScreen = s => Console.WriteLine(s); // use them printToScreen(convertIntToString(getOne()));
I found this bit of code awhile ago (can’t remember who to attribute it to). It’s quite ingenius, using a Category to allow the creation of a mutable array that does no retain/release by backing it with a CFArray with proper callbacks. @implementation NSMutableArray (WeakReferences) + (id)mutableArrayUsingWeakReferences { return [self mutableArrayUsingWeakReferencesWithCapacity:0]; } + (id)mutableArrayUsingWeakReferencesWithCapacity:(NSUInteger)capacity { … Read more
Yes, UIApplication is a singleton, and uses the normal singleton pattern for Objective-C: [UIApplication sharedApplication]; You can get your delegate class directly from it: MyAppDelegate *delegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
It’s not guaranteed either way. From what I remember of the current MS implementation: A lambda expression which doesn’t capture any variables is cached statically A lambda expression which only captures “this” could be captured on a per-instance basis, but isn’t A lambda expression which captures a local variable can’t be cached Two lambda expressions … Read more
From http://msdn.microsoft.com/en-us/library/system.delegate.aspx: The Delegate class is the base class for delegate types. However, only the system and compilers can derive explicitly from the Delegate class or from the MulticastDelegate class. It is also not permissible to derive a new type from a delegate type. The Delegate class is not considered a delegate type; it is … Read more
The datasource supplies the data, the delegate supplies the behavior. In MVC, datasource is in the model layer and the delegate is in the control layer. Actually, on second thought, the datasource is usually controller that is lower down, closer to the model. I don’t think I’ve ever used a model object as my datasource.
You can use System.Linq.Expressions.Expression.GetDelegateType method: using System; using System.Linq; using System.Linq.Expressions; using System.Reflection; class Program { static void Main() { var writeLine = CreateDelegate(typeof(Console).GetMethod(“WriteLine”, new[] { typeof(string) })); writeLine.DynamicInvoke(“Hello world”); var readLine = CreateDelegate(typeof(Console).GetMethod(“ReadLine”, Type.EmptyTypes)); writeLine.DynamicInvoke(readLine.DynamicInvoke()); } static Delegate CreateDelegate(MethodInfo method) { if (method == null) { throw new ArgumentNullException(“method”); } if (!method.IsStatic) { throw … Read more
This introduces a lambda function (anonymous delegate) with no parameters, it’s equivalent to and basically short-hand for: delegate void () { return action.GenerateDescription(); } You can also add parameters, so: (a, b) => a + b This is roughly equivalent to: delegate int (int a, int b) { return a + b; }
The two are equivalent, the compiler converts OnAdd(“It Happened”); into OnAdd.Invoke(“It Happened”); for you. I guess it’s a matter of preference, however I personally prefer the terser form. As an aside, it is generally preferable to take a local copy of a class level delegate before invoking it to avoid a race condition whereby OnAdd … Read more
As of this commit Moq now supports the mocking of delegates, for your situation you would do it like so: var fooMock = new Mock<Foo>(); var a = new A(fooMock.Object); Then you can verify the delegate was invoked: fooMock.Verify(f => f(5), Times.Once); Or: fooMock.Verify(f => f(It.IsAny<int>()), Times.Once);