proxy
- (proxy class-and-interfaces args & fs)
class-and-interfaces - a vector of class names args - a (possibly empty) vector of arguments to the superclass constructor. f => (name [params*] body) or (name ([params*] body) ([params+] body) ...) Expands to code which creates a instance of a proxy class that implements the named class/interface(s) by calling the supplied fns. A single class, if provided, must be first. If not provided it defaults to Object. The interfaces names must be valid interface types. If a method fn is not provided for a class method, the superclass method will be called. If a method fn is not provided for an interface method, an UnsupportedOperationException will be thrown should it be called. Method fns are closures and can capture the environment in which proxy is called. Each method fn takes an additional implicit first arg, which is bound to 'this. Note that while method fns can be provided to override protected methods, they have no other access to protected members, nor to super, as these capabilities cannot be proxied.
© Rich Hickey. 保留所有权利。 Eclipse 公共许可证 1.0
5 Examples
;; adding a mouse-pressed callback to a Swing component: (defn add-mousepressed-listener [component f & args] (let [listener (proxy [MouseAdapter] [] (mousePressed [event] (apply f event args)))] (.addMouseListener component listener) listener))
;; BUG: proxy dispatches *only* on name, not arity: user=> (let [p (proxy [java.io.InputStream] [] (read [] -1))] (println (.read p)) (println (.read p (byte-array 3) 0 3))) -1 ArityException Wrong number of args (4) passed to: core$eval213$fn clojure.lang.AFn.throwArity (AFn.java:437)
;; You can, however, provide multiple-arity functions to get some support ;; for overloading user> (let [p (proxy [java.io.InputStream] [] (read ([] 1) ([^bytes bytes] 2) ([^bytes bytes off len] 3)))] (println (.read p)) (println (.read p (byte-array 3))) (println (.read p (byte-array 3) 0 3))) 1 2 3 nil
;; a simple example (defn f [& i] (proxy [clojure.lang.ISeq][] (seq [] (sort i)) (toString [] (apply str (interpose "-" i))))) (seq (f 4 3 2 1)) ;;=> (1 2 3 4) (str (f 4 3 2 1)) ;;=> "4-3-2-1"
