Dynamically cast in iOS?

Question

Let's say I have:

ThisClass *castHere = [[ThisClass alloc] init];

But I effectively want:

ThisClassChosenAtRuntime *castHere = [[ThisClassChosenAtRuntime alloc] init];

I'm sure there is some smarter way to go about this. But this is the result I'm after. I already have castHere subjected to setValue forKey statements. But I want to dynamically setup *castHere.

your question is not clear. Do you want to change the name of ur class? — Frans Raharja Kurniawan, Sep 22 '14 at 17:02
A partial answer is to use `id castHere = ...` but the rest of it depends on how you're choosing which class you want to `alloc`. — Phillip Mills, Sep 22 '14 at 17:04
I have several classes and want to choose which one is applied to *castHere. There are different property names with each class. — Bill3, Sep 22 '14 at 17:05
Repeating, how do you choose? If it's just a simple `if` or `switch` or something, then the `id` trick is all you need. If you're trying to decide on a class by using its name (as a string) things get more complicated. — Phillip Mills, Sep 22 '14 at 17:08
I'd like to pass the name over as a string. I could use `if` statements or `switch` and get through this. But I'm looking to future proof without revisiting this method. Sorry for making admdrew work overtime. :) — Bill3, Sep 22 '14 at 17:15
possible duplicate of [Objective-C class -> string like: \[NSArray className\] -> @"NSArray"](http://stackoverflow.com/questions/2331983/objective-c-class-string-like-nsarray-classname-nsarray) — Craig Otis, Sep 22 '14 at 17:23
You can't "cast" with a variable type. Period. But there's absolutely no need to. — Hot Licks, Sep 22 '14 at 17:32

score 3 · Accepted Answer · answered Sep 22 '14 at 17:18

If you can build up the class name as a string, then it's easy.

NSString *className = @"ThisClassChosenAtRuntime";
id object = [[NSClassFromString(className) alloc] init];

Note that the return type is id. You can call any method from an instance of type id.

For something more type safe and if you can rely on a base class than you can.

NSString *className = @"ThisClassChosenAtRuntime";
MyBaseClass *object = [[NSClassFromString(className) alloc] init];

That's it! Thanks Jeffery and Phillip. – Bill3 Sep 22 '14 at 17:40 — Bill3, Sep 22 '14 at 17:40

Dynamically cast in iOS?

1 Answers1