在Applescript中检查字符串中包含字符串的次数

set sourceString to "This is a test string"
set targetString to "is"
if sourceString contains targetString then
    display dialog "字符串中包含目标字符串"
else
    display dialog "字符串中不包含目标字符串"
end if

set sourceString to "This is a test string"
set targetString to "is"
set countOccurrences to 0
set offsetValue to 1

repeat
    set offsetValue to offset of targetString in sourceString starting at offsetValue
    if offsetValue is 0 then exit repeat
    set countOccurrences to countOccurrences + 1
    set offsetValue to offsetValue + 1
end repeat

display dialog "字符串中包含目标字符串的次数为：" & countOccurrences