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So I have defined say a keyword:
(def a :hello)
how do I check that it implements the IFn interface?
783
A class implements an interface if it declares the interface in its implements clause, and provides method bodies for all of the interface's methods. So one way to define an abstract data type in Java is as an interface, with its implementation as a class implementing that interface.
The java “instanceof” operator is used to test whether the object is an instance of the specified type (class or subclass or interface). It is also known as type comparison operator because it compares the instance with type. It returns either true or false.
To declare a class that implements an interface, include an implements keyword in the class declaration.
Interface types act like class types. You can declare variables to be of an interface type, you can declare arguments of methods to accept interface types, and you can even specify that the return type of a method is an interface type.
For the general case, you can use the instance? predicate:
(instance? <class-or-interface> <object>)
Quoting the documentation:
(instance? c x)evaluates x and tests if it is an instance of the class c. Returns true or false.
For example:
(instance? java.lang.String "test")
> true
(instance? java.io.Serializable "test")
> true
For the code in the question, do something like this:
(instance? package.of.IFn a)
Or, as has been pointed out in the comments, for the very specific case of asking if a is an instance of IFn this will work:
(ifn? a)
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