CODEWITHSUNDEEP
iosobjective-cswiftclassinheritance
rollingcodes
rollingcodes

Reputation: 16008

iOS difference between isKindOfClass and isMemberOfClass

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.

Upvotes: 161

Views: 43254

Answers (6)

Sebastian Celis
Sebastian Celis

Reputation: 12195

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.

Upvotes: 276

Art Swri
Art Swri

Reputation: 2804

Because of class clusters, isMemberOfClass can give you an answer you might not expect. In many cases your best choice is more likely to be -(BOOL)conformsToProtocol:(SEL)aSelector or - (BOOL)conformsToProtocol:(Protocol*)aProtocol. I.e, it's better to test these if they can answer your need rather than testing class/subclass.

See apple doc for NSObject class and protocol:

http://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/Reference/Reference.html#//apple_ref/occ/cl/NSObject

http://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Protocols/NSObject_Protocol/Reference/NSObject.html#//apple_ref/occ/intf/NSObject

Upvotes: 0

Ishu
Ishu

Reputation: 12787

isKindOfClass-> return YES when the object is instance of that class or instance of a class which is inherited from it.

isMemberOfClass: return YES when the object is instance of that class but No in case: instance of a class which is inherited from it.

example is good enough in jtbandes answer.

Upvotes: 2

Alex Terente
Alex Terente

Reputation: 12036

isKindOfClass: Returns a Boolean value that indicates whether the receiver is an instance of given class or an instance of any class that inherits from that class.

isMemberOfClass: Returns a Boolean value that indicates whether the receiver is an instance of a given class.

Upvotes: 9

jtbandes
jtbandes

Reputation: 118691

  • 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

Upvotes: 84

kennytm
kennytm

Reputation: 523344

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.

Upvotes: 48

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