Monotouch: convert an Object to NSObject

问题:

How is it possible to convert an Object instance to NSObject one?

I've created a NSDictionary from

NSDictionary.FromObjectAndKey();

This method wants an NSObject but I have custom object to pass in:

int key = 2341;
var val = new MyClass();
NSDictionary.FromObjectAndKey(val, key); // obviously it does not work!!

How to fix this? Thank you in advance.

回答1:

You can not convert an arbitrary object into an NSObject. The NSObject.FromObject will try to wrap common data types like numbers, strings, rectangles, points, transforms, and a handful of other .NET types into their equivalent NSObject types.

In your particular example, "MyClass" would have to derive from an NSObject before you could use it in the NSDictionary.

回答2:

The easiest solution I could find was to wrap the .Net object in an NSObject, then unwrap as needed.

public class NSObjectWrapper : NSObject
{
    public object Context;

    public NSObjectWrapper (object obj) : base()
    {
        this.Context = obj;
    }

    public static NSObjectWrapper Wrap(object obj)
    {
        return new NSObjectWrapper(obj);
    }
}

Example use:

// wrap
var myNSObj = NSObjectWrapper.Wrap(new MyClass());
// unwrap
var myObj = myNSObj.Context as MyClass;

回答3:

This is the way:

NSDictionary.FromObjectAndKey(NSObject.FromObject(val), NSObject.FromObject(key));