I did this for a small project to get something up and running to demo to a client. Once I got into specifics of business rules, validation and other considerations, I ended up having to override the CRUD methods from my base class so it didn’t pan out as a long term implementation. I ran … Read more
Not really; C# only supports no-args constructor constraints. The workaround I use for generic arg constructors is to specify the constructor as a delegate: public T MyGenericMethod<T>(MyClass c, Func<MyClass, T> ctor) { // … T newTObj = ctor(c); // … } then when calling: MyClass c = new MyClass(); MyGenericMethod<OtherClass>(c, co => new OtherClass(co));
Nope, I’m afraid not. The only things you can do with constraints are: where T : class – T must be a reference type where T : struct – T must be a non-nullable value type where T : SomeClass – T must be SomeClass or derive from it where T : ISomeInterface – T … Read more
Your approach of using a generic method is strictly more powerful than a version with wildcards, so yes, your approach is possible, too. However, the tutorial does not state that using a wildcard is the only possible solution, so the tutorial is also correct. What you gain with the wildcard in comparison to the generic … Read more
Here’s a place where this would be useful. Say you have a strongly-typed OptionKey<T> for declaring options. public static class DefaultOptions { public static OptionKey<bool> SomeBooleanOption { get; } public static OptionKey<int> SomeIntegerOption { get; } } Where options are exposed through the IOptions interface: public interface IOptions { /* since options have a default … Read more
What you mean by this part is possible: new AnimalContext<a.GetType()>(); Obviously that exact syntax is wrong, and we’ll get to that, but it is possible to construct an instance of a generic type at runtime when you don’t know the type parameters until runtime. What you mean by this part is not: AnimalContext<a.GetType()> a_Context That … Read more
Instantiating a generic type with different type arguments produces two new different named types. Note that every time you supply a type argument, including in function arguments or return types, you are instantiating the generic type: // Props is instantiated with type argument ‘Generic’ func Problem() Props[Generic] { return ExampleProps } Therefore Props[Example] is just … Read more
A core type, for an interface (including an interface constraint) is defined as follows: An interface T has a core type if one of the following conditions is satisfied: There is a single type U which is the underlying type of all types in the type set of T or the type set of T … Read more
Dart does not support instantiating from a generic type parameter. It doesn’t matter if you want to use a named or default constructor (T() also does not work). There is probably a way to do that on the server, where dart:mirrors (reflection) is available (not tried myself yet), but not in Flutter or the browser. … Read more
There are two separate issues here. A List<Object> can in fact take any object as you say. A List<Number> can take at least Number objects, or of course any subclasses, like Integer. However a method like this: public void print(List<Number> list); will actually only take a List which is exactly List<Number>. It will not take … Read more