Question

Is it possible in Objective C to modify an object type at runtime without the compiler complaining?

e.g.

id object;

in an init method

initWithType:(someEnumType) type

then depending on type set the object to a class type.

How is this done without the compiler flagging errors that object does not declare someMethod?

Answer 1

The most common way to do something like that is in a factory method, rather than an initializer:

typedef enum {
    etString,
    etNumber
} EnumType;

@implementation MyFactory

+(id)makeNewObjectWithType:(EnumType)et {
    id res;
    switch (et) {
        case etString:
            res = [NSString string];
            break;
        case etNumber:
            res = [NSNumber numberWithInt:12345];
            break;
        default:
            res = nil;
            break;
    }
    return res;
}

@end