what is the difference between iskindofclass and ismemberofclass [duplicate]

Question

What is the difference between the isKind(of aClass: AnyClass) and the isMember(of aClass: AnyClass) functions in Swift?

Original Question in Objective-C

What is the difference between the isKindOfClass:(Class)aClass and the isMemberOfClass:(Class)aClass functions? I know it is something small like, one is global while the other is an exact class match but I need someone to specify which is which please.

Answer 1

isKindOfClass: returns YES if the receiver is an instance of the specified class or an instance of any class that inherits from the specified class.

isMemberOfClass: returns YES if, and only if, the receiver is an instance of the specified class.

Most of the time you want to use isKindOfClass: to ensure that your code also works with subclasses.

The NSObject Protocol Reference talks a little more about these methods.

Answer 2

• isKindOfClass: indicates whether an object inherits from a given class
• isMemberOfClass: indicates whether an object is an instance of a given class.

---

[[NSMutableData data] isKindOfClass:[NSData class]]; // YES
[[NSMutableData data] isMemberOfClass:[NSData class]]; // NO

Answer 3

Suppose

@interface A : NSObject 
@end

@interface B : A
@end

...

id b = [[B alloc] init];

then

[b isKindOfClass:[A class]] == YES;
[b isMemberOfClass:[A class]] == NO;

Basically, -isMemberOfClass: is true if the instance is exactly of the specified class, while -isKindOfClass: is true if the instance is exactly of the specified class or if one of the instance's ancestors is of the specified class.

-isMemberOfClass: is seldom used.