Clojure使用映射值交换原子
我想将映射的值关联到原子中。 我可以这样做:Clojure使用映射值交换原子,clojure,atomic,Clojure,Atomic,我想将映射的值关联到原子中。 我可以这样做: (defonce config (atom {})) (swap! config assoc :a "Aaa") (swap! config assoc :b "Bbb") 但是它是重复的,并且多次调用swap。 我想这样做: (swap! config assoc {:a "Aaa" :b "Bbb"}) ;; this doesn't work : ;; Exception in thr
(defonce config (atom {}))
(swap! config assoc :a "Aaa")
(swap! config assoc :b "Bbb")
但是它是重复的,并且多次调用swap代码>。
我想这样做:
(swap! config assoc {:a "Aaa"
:b "Bbb"})
;; this doesn't work :
;; Exception in thread "main" clojure.lang.ArityException: Wrong number of args (2) passed to: core$assoc
如何做到这一点?请参阅assoc
的文档:
=> (doc assoc)
-------------------------
clojure.core/assoc
([map key val] [map key val & kvs])
assoc[iate]. When applied to a map, returns a new map of the
same (hashed/sorted) type, that contains the mapping of key(s) to
val(s). When applied to a vector, returns a new vector that
contains val at index. Note - index must be <= (count vector).
nil
顺便说一下,您应该始终将对atom的更新隔离为单个交换代码>。通过如上所述进行两次交换,您将允许其他线程潜在地破坏引用的数据。一次交换代码>保持一切原子
N.B.merge
的行为与您想象的一样:
user=> (merge {} {:a 1 :b 1})
{:a 1, :b 1}
user=> (let [x (atom {})]
#_=> (swap! x merge {:a 1 :b 2})
#_=> x)
#object[clojure.lang.Atom 0x1be09e1b {:status :ready, :val {:a 1, :b 2}}]
user=> (merge {} {:a 1 :b 1})
{:a 1, :b 1}
user=> (let [x (atom {})]
#_=> (swap! x merge {:a 1 :b 2})
#_=> x)
#object[clojure.lang.Atom 0x1be09e1b {:status :ready, :val {:a 1, :b 2}}]