alexanderjamesking · October 7, 2021 20:02 · May 13, 2013
diff --git a/errors.clj b/errors.clj
@@ -0,0 +1,114 @@
+(ns example.errors)
+
+(defn clean-address [params]
+  "Ensure (params :address) is present"
+  (if (empty? (params :address))
+    [nil "Please enter your address"]
+    [params nil]))
+
+(defn clean-email [params]
+  "Ensure (params :email) matches *@*.*"
+  (if (and (params :email) (re-find #".*@.*\..*" (params :email)))
+    [params nil]
+    [nil "Please enter an email address"]))
+
+
+(defn clean-phone [params]
+  "Ensure phone number matches (555) 555-5555"
+  (if (and (params :phone) (re-find #"\([0-9]{3}\) [0-9]{3}-[0-9]{4}" (params :phone)))
+    [params nil]
+    [nil "Please enter your phone number in (555) 555-5555 format."]))
+
+
+(defn clean-state [params]
+  "Ensure state is one of OR or WA. Cascadians unite!"
+  (case (params :state)
+    "WA" [params nil]
+    "OR" [params nil]
+    [nil "We only want people from Oregon or Washington, for some reason."]))
+
+; And our examples
+
+(defn clean-contact-bad [params]
+  (let [[params err] (clean-email params)
+        [params err] (if (nil? err) (clean-address params) [nil err])
+        [params err] (if (nil? err) (clean-phone params) [nil err])
+        [params err] (if (nil? err) (clean-state params) [nil err])]
+    [params err]))
+
+(defn apply-or-error [f [val err]]
+  (if (nil? err)
+    (f val)
+    [nil err]))
+
+(defn clean-contact-ok [params]
+  (let [result (clean-email params)
+        result (apply-or-error clean-address result)
+        result (apply-or-error clean-phone result)
+        result (apply-or-error clean-state result)]
+    result))
+
+(defn clean-contact-good [params]
+  (->> (clean-email params)
+       (apply-or-error clean-address)
+       (apply-or-error clean-phone)
+       (apply-or-error clean-state)))
+
+(defmacro err->> [val & fns]
+  (let [fns (for [f fns] `(apply-or-error ~f))]
+    `(->> [~val nil]
+          ~@fns)))
+
+(defn clean-contact [params]
+  (err->> params
+          clean-email
+          clean-address
+          clean-phone
+          clean-state))
+
+
+(comment
+(use 'clojure.test)
+
+(is (= (clean-address {})
+       [nil "Please enter your address"]))
+(is (= (clean-address {:address "123 Fake St."})
+       [{:address "123 Fake St."} nil]))
+
+(is (= (clean-email {:email "test"})
+       [nil "Please enter an email address"]))
+(is (= (clean-email {})
+       [nil "Please enter an email address"]))
+(is (= (clean-email {:email "test@test.com"})
+       [{:email "test@test.com"} nil]))
+
+(is (= (clean-phone {})
+       [nil "Please enter your phone number in (555) 555-5555 format."]))
+(is (= (clean-phone {:phone "1-800-555-1234"})
+       [nil "Please enter your phone number in (555) 555-5555 format."]))
+(is (= (clean-phone {:phone "(800) 555-1234"})
+       [{:phone "(800) 555-1234"} nil]))
+
+(is (= (clean-state {:state "CA"})
+       [nil "We only want people from Oregon or Washington, for some reason."]))
+(is (= (clean-state {:state "WA"})
+       [{:state "WA"} nil]))
+
+(is (= (clean-contact {})
+       [nil "Please enter an email address"])) 
+
+(is (= (clean-contact {:email "test@test.com"})
+       [nil "Please enter your address"])) 
+
+(is (= (clean-contact {:email "test@test.com" :address "123 Fake St."})
+       [nil "Please enter your phone number in (555) 555-5555 format."]))
+
+(is (= (clean-contact {:email "test@test.com" :address "123 Fake St." :phone "(800) 555-1234"})
+       [nil "We only want people from Oregon or Washington, for some reason."]))
+
+(is (= (clean-contact {:email "test@test.com" :address "123 Fake St." :phone "(800) 555-1234"})
+       [nil "We only want people from Oregon or Washington, for some reason."]))
+
+(is (= (clean-contact {:email "test@test.com" :address "123 Fake St." :phone "(800) 555-1234" :state "WA"})
+       [{:email "test@test.com" :address "123 Fake St." :phone "(800) 555-1234" :state "WA"} nil]))
+)
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