Implementation and Inheritance of objc lightweight generics

objc-lightweight-generics.m

// Header File

NS_ASSUME_NONNULL_BEGIN

  // No asterisk after DataType
@interface BaseCell<DataType> : UICollectionViewCell

- (DataType)data;
- (void)bindData:(DataType)data;

@end


  // Specify generic type in subclass
@interface MyCell: BaseCell

- (void)bindData:(__kindof UIView *)data;

@end

NS_ASSUME_NONNULL_END
  
  
  
// Implementation File
  
  // Can not use generic type, use `id` instead.
@implementation BaseCell
- (id)data {
    return @"no data";
}
- (void)bindData:(id)data {
    [NSObject doesNotRecognizeSelector:_cmd];
}

@end

@implementation MyCell
- (void)bindData:(__kindof UIView *)data {
    NSLog(@"bindData");
}
@end
  
  
// Another file
  
MyCell *m = [MyCell new];
[m bindData:[UIView new]];
[m bindData:@""]; // Warning: Incompatible pointer types sending

Further more, generic type can have base class or protocol conforming constraints.
Refer to http://drekka.ghost.io/objective-c-generics/ and https://miqu.me/blog/2015/06/09/adopting-objectivec-generics/

According to Apple's documentation:

Aside from than these Foundation collection classes, Objective-C lightweight generics are ignored by Swift. Any other types using lightweight generics are imported into Swift as if they were unparameterized.