How to do multiple interfaces in Objective C?

How can I do the following things in Objective C (the examples below are in p开发者_JAVA技巧seudo-code):

1. interface A extends B, C

2. interface A

interface B

class X inplemements A, B

3. interface A

class X implements A

class Y implements A

interface B

class Z extends Y implements B

thanks!

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Sounds like homework, you should take the first move: http://en.wikipedia.org/wiki/Objective-C

look at 2.2 Interfaces and implementations

MyClass extends Class

 @interface MyClass : Class { }
 @end

MyClass extends Class implements Interface1 & Interface2

 @interface MyClass : Class <Interface1, Interface2> {}
 @end