Question

My app has a large number of view controllers declared in the interface for example:

ViewController_1_0 *viewController_1_0
ViewController_1_1 *viewController_1_1
ViewController_1_2 *viewController_1_2
etc ...

(I realize the underscores are not a good Cocoa coding convention for class names and will change that.)

My intent is to present appropriate controller views based on the current UIStepper value.

Rather than do conditional tests for each of the stepper values and then perform a separate lazy instantiation of the controller object using the “hard coded” view controllers I am trying to have code appearing once using strings constructed based upon the current stepper value.

I’ve figured out (with help from Use a Class name stored in a variable to call a Class method?) how to set up the Class name: I’ve declared a property:

@property(strong, nonatomic) Class classStringClass;

And then after constructing the variable string for the class, I do:

classStringClass = NSClassFromString(classString);

Where classString is the constructed string using the stepper value, equivalent to ViewController_1_0, for example.

I’ve also declared a property for the ivar as:

@property (strong, nonatomic) NSString *classInstanceString;

Therefore I do:

if(!classInstanceString) {
   classInstanceString = [[classStringClass alloc] initWithNibName:classString bundle:nil];
}

Where I am stuck is how to code for the ivar for the controllers, i.e., classInstanceString constructed to be the equivalent of the ivar viewController_1_0 (or whatever based on the stepper value) declared in the interface. Once I get out of the lazy instantiation if statement and then code to access properties of classInstanceString, for example:

classInstanceString.view.hidden = NO;

classInstanceString understandably gets an error “Property ‘view’ not found on object of type ‘NSString'”.

How do I declare ‘classInstanceString’ (or another variable, say ‘classInstanceVariable’ containing the classInstanceString value) so when instantiating it, it is the ivar of classStringClass and has access to the class properties, to use subsequent to the instantiation of the class ? I surmise that it should be a different type than an NSString, but what type would that be, or is there another way to do this ?

Answer 1

If you just need basic UIViewController ivars you could always cast it to a UIViewController.

UIViewController *vc = (UIViewController *)[[classStringClass alloc] initWithNibName:classString bundle:nil];

[vc view];// works!

Or if you need custom ivars it would be a good idea if they all extended a base class (or protocol) like so:

MyBaseViewController *vc = (MyBaseViewController *)[[classStringClass alloc] initWithNibName:classString bundle:nil];

[vc customVar]; //works