问题描述
我需要每500毫秒定期将缓存保存到磁盘上，该怎么办？
我尝试的代码未正确编译。另外，似乎asyncCheck应该用于错误检查。
import tables,os,asyncdispatch
var cache = init_table[string,int]()
proc save(cache: Table[string,int]): Future[void] {.async.} =
echo cache
addTimer(
timeout = 500,oneshot = false,cb = proc() = discard cache.save()
)
for i in (0..3):
cache["a"] = i
echo cache
sleep 1000
解决方法
我认为这是您所追求的事情
import tables,asyncdispatch,strformat
#global,GC'd variable,careful!
var cache = initTable[string,int]()
proc save(){.async.} =
while true:
echo &"writing cache:{cache}"
await sleepAsync(500)
#just some fake data sources
proc write1(){.async.} =
await sleepAsync(900)
for i in 0..99:
cache["a"]=i
await sleepAsync(20)
#that happen at various rates
proc write2(){.async.} =
for i in 0..99:
cache["b"]=i
await sleepAsync(33)
#asyncCheck when we're not interested in the Future from a proc
#it will raise an Exception if the proc has an error
asyncCheck save() #save starts running asynchronously
echo "but we can still run other code"
waitFor: #blocks here until both write1 and write2 finish
write1() and write2()
echo "writing is done but save is still running"
cache["c"]=17
#os.sleep would block the whole thread,including save so instead
waitFor(sleepAsync(500)) #wait for save to echo one more time
echo "quit"
输出类似：
writing cache:{:}
but we can still run other code
writing cache:{"b": 15}
writing cache:{"b": 30,"a": 4}
writing cache:{"b": 45,"a": 29}
writing cache:{"b": 59,"a": 54}
writing cache:{"b": 74,"a": 78}
writing cache:{"b": 89,"a": 99}
writing is done but save is still running
writing cache:{"b": 99,"c": 17,"a": 99}
quit