(dorun coll) (dorun n coll)
When lazy sequences are produced via functions that have side effects, any effects other than those needed to produce the first element in the seq do not occur until the seq is consumed. dorun can be used to force any effects. Walks through the successive nexts of the seq, does not retain the head and returns nil.
user=> (dorun 5 (repeatedly #(println "hi")))
hi
hi
hi
hi
hi
hi
nil
user=> (let [x (atom 0)]
(dorun (take 10 (repeatedly #(swap! x inc))))
@x)
10
user=> (dorun (map #(println "hi" %) ["mum" "dad" "sister"]))
hi mum
hi dad
hi sister
nil
;;map a function which makes database calls over a vector of values
user=> (map #(db/insert :person {:name %}) ["Fred" "Ethel" "Lucy" "Ricardo"])
JdbcSQLException The object is already closed [90007-170] org.h2.message.DbE
xception.getJdbcSQLException (DbException.java:329)
;;database connection was closed before we got a chance to do our transactions
;;lets wrap it in dorun
user=> (dorun (map #(db/insert :person {:name %}) ["Fred" "Ethel" "Lucy" "Ricardo"]))
DEBUG :db insert into person values name = 'Fred'
DEBUG :db insert into person values name = 'Ethel'
DEBUG :db insert into person values name = 'Lucy'
DEBUG :db insert into person values name = 'Ricardo'
nil