<div style><div>Hey Haskellers, I had a design question:</div><div><br></div><div>I'm using Haskell for the first time for something other than a simple toy application. I notice I'm coming up with a lot of IO based APIs that looks something like this:</div>
<div><br></div><div>type UserInfo = (String, String) -- (name, password)</div><div><br></div><div>getMagicNumberFromHTTPServer :: UserInfo -> IO (Maybe Int)</div><div>getMagicNumberFromHTTPServer user = do</div><div> let curlHTTPRequest = ... --Setup curl HTTP request</div>
<div> httpRepsponse <- ... -- Make curl HTTP request</div><div> return $ tryGetMagicNumberFromResponse httpResponse</div><div><br></div><div>I like this API, because it's easy to understand. However, I find it hard to test. In OO land, I'd create a mock CurlHTTPRequest object and pass that into the magic number logic and test for the correct usage of the curl library. Is there a FP way of achieving the same goals?</div>
<div><br></div><div>I suppose given the example above I could break down the above into several smaller pure functions and test them. I don't know if this strategy will hold-up when dealing with more complex monads.</div>
<div><br></div><div>Thanks for your time,</div><div>Dave</div></div>