我已经有一个代码,但是它一直在选择列表中的第一个文件,并且变得令人不快。我不知道该怎么办。
func detachListener() {
let listener = database.collection("Users").document(currentUserUUID!).collection("Transactions").addSnapshotListener { querySnapshot, error in
if error != nil{
print(error as Any)
}
}
listener.remove()
}
答案 0 :(得分:1)
大小为30位的rand(值从0到2 ^ 30-1以n为模)
@echo off
setlocal EnableDelayedExpansion
pushd c:\"source"\somefolder
set "n=0"
for /f "tokens=*" %%f in ('dir /b /a-d *.*') do (
rem number files from 0 and use full filename with spaceses
set "file[!n!]=%%~ff"
set /a "n+=1"
)
popd
if %n% leq 32768 ( set /a "rand=%random%%%n%"
) else set /a "rand=((%random%<<15)+%random%)%%n%"
move "!file[%rand%]!" C:\destination\somefolder
pause
endlocal