Passing a Class as parameter and instantiating an object using this class - ios

Question

Is this possible, I searched the net and found no answer to this. My senior also said that this is not possible.
I'm trying to add this as a category, so I want to extract 4 types of objects out of it, all of them uses the same code, it's just the classes that differ so I thought of this:
- (NSDictionary *) getObjectsOfClass:(Class)class
{
NSMutableDictionary *objDict = [NSMutableDictionary dictionary];
[self.subviews enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj isKindOfClass:class]) {
/*
Is there a way to do this?
class *label = (class *)obj;
*/
}
}];
return objDict;
}
So is there a way to make this work? It's ugly to see 4 functions with almost the same codes, you agree right?

Answer 1

What about passing class name as string & creating object out of it. May be like this
-(NSArray *)arrayOfObjectsForClass:(NSString *)className{
NSMutableArray *objectArray = [[NSMutableArray alloc]init];
CGFloat yAxis = 10;
for(int i =0; i<5; i++){
id object = [[NSClassFromString(className) alloc]initWithFrame:CGRectMake(0, yAxis, 100, 50)];
[object setTitle:[NSString stringWithFormat:#"Button %d", i+1]];
[objectArray addObject:object];
yAxis+= 60;
}
return objectArray;
}

Answer 2

Because of you said "But I'm adding it to uiview, to get the textfields, labels, pickerviews etc, so that I can just call [self.view getObjectsOfClass:[UILabel class]"
For this code
[self.view getObjectsOfClass:[UILabel class]];
it will return all its UILabel immediate children of it.
- (NSMutableArray *) getObjectsOfClass:(Class)class
{
NSMutableArray *objArray = [NSMutableArray array];
[self.subviews enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
// All visible things are inherited from UIView. Tag property is belongs to UIView
// UILabel are inherited from UIView
if ([self isKindOfClass:[UIView class]] && [obj isKindOfClass:class]) {
UIView *aView = (UIView*)obj;
if (aView.tag == 100) {
//This is the view with tag 100
}
[objArray addObject:obj];
}
}];
return objArray;
}

Answer 3

If all of them are derived from a common base class, you can cast them into that common base class. If few functions are not available then create a category of that common base class and add those common functions into it. This will allow you to have single code block rather than 4 different one.

Answer 4

You can instantiate your class argument like this:
id newInstance = [class new];
What you cannot syntactically do is using class * as a way to tell the compiler which type your local variable is. But this is also not required, thanks to Objective C dynamics typing capabilities.
In other words, there is not reason to cast to class (and you cannot do that; class is only known at runtime, casting has effect at compile time).
EDIT:
If you know a base class common to all of your classes, e.g. UIView, then you could do:
UIView* newInstance = obj;
then access its properties, e.g.:
if (newInstance.tag ==…)
Or you could use message sending instead of properties and do:
if ([obj tag] == ...)