Question

I’m working on some java library wrapper.
We have some object with methods and can invoke them with (.method object ...). I want to create more convenient api with number of functions (method object ...).

I wrote a simple macro:

(defmacro ^{:private true} gen-method [method & argv]
  `(def ~method (memfn ~method ~@argv)))

Now I can invoke (gen-method charAt i) for example and after that I can use (charAt "string" 1).

But I have a lot of method to generate and want to use something like:

(map #(gen-method (-> %1 name symbol arg)) [:charAt :substring ...])

But this is not working. Next example is not working too:

(map #(let [fname (-> %1 name symbol)] (gen-method fname arg)) [:charAt :substring ...])

What I need to change in macro or add something for correct behaviour ?

Thanks.

Answer 1

You will have to take the map operation inside the macro itself as the map operation should happen at compile time i.e form expanding time and not at runtime.

Something like below:

(defmacro ^{:private true} gen-methods [methods]
`(do 
       ~@(map (fn [[x & i]] (let [m (-> x name symbol)] `(def ~m (memfn ~m ~@i)) )) methods)))

(gen-methods [ [:charAt i] [:substring i]])