I'd like to create a list depending on the results of some functions. In Java (my background), I'd do something like:
List<String> messages = ...
if(condition 1)
messages.add(message 1);
if(condition 2)
messages.add(message 2);
...
if(condition N)
messages.add(message N);
In clojure, I think I'll need to create a list using let like the following (just dummy example):
(let [result
(vec
(if (= 1 1) "message1" "message2")
(if (= 1 0) "message3" "message4"))]
result)
I've also checked cond but I need to be appending the elements to the list considering all the validations (and cond breaks after one condition is satisfied).
Which way should I follow to achieve this?
If you want them to be conditionally added like in the Java example, you could use cond->, which does not short circuit:
(let [messages []]
(cond-> messages ; Conditionally thread through conj
(= 1 1) (conj "Message1")
(= 0 1) (conj "Message2")
(= 0 0) (conj "Message3")))
=> ["Message1" "Message3"]
If you want to conditionally add one or the other like your second example suggests however, you could just use plain conj with some if expressions:
(let [messages []]
(conj messages
(if (= 1 1) "Message1" "Message2")
(if (= 0 1) "Message3" "Message4")))
=> ["Message1" "Message4"]
And I'll note that your original attempt almost worked. Instead of vec, you could have used vector, or just a vector literal:
(let [messages [(if (= 1 1) "Message1" "Message2")
(if (= 1 0) "Message3" "Message4")]]
messages)
=> ["Message1" "Message4"]
Although, this is would only be beneficial if you didn't already have a messages populated that you wanted to add to. If that was the case, you'd have to use concat or into:
(let [old-messages ["old stuff"]
messages [(if (= 1 1) "Message1" "Message2")
(if (= 1 0) "Message3" "Message4")]]
(into old-messages messages))
=> ["old stuff" "Message1" "Message4"]