我想从名为cache_image
的表中检索数据,但我不知道该怎么做,我在这里遇到错误。
func checkCachedImages() ->Bool{
database?.open()
var count = Int()
for i in images{
do{
if let value = database?.executeQuery("SELECT DOWNLOAD_URL FROM CACHED_IMAGE WHERE IMAGE_NAME = ?", withArgumentsIn: [i]){
while value.next(){
print(value.string(forColumn: "IMAGE_NAME"))
print(value.string(forColumn: "DOWNLOAD_URL"))
count += 1
print(count)
}
}
}catch {
print(error)
}
}
database?.close()
if count == images.count{
print("The count is \(count)")
return true
}
return false
}
我有一个名为cached_image
的表和两个名为image_name
和download_url
的列,但是当我尝试使用它时
print(value.string(forColumn: "IMAGE_NAME")
它显示警告:
找不到image_name,对于列“download_url”,它显示“Optional(”“)”
请帮我解决这个问题。
你不能从结果中读取image_name
,因为它不是SELECT
条款的一部分,但你不需要它,因为你可以从i
得到它
var numberOfRows = 0
var urls: [String] = ()
print("Image name: \(i)")
if let result = try database?.executeQuery("SELECT download_url FROM CACHED_IMAGE WHERE IMAGE_NAME = ?", values: [i]) {
while result.next() {
numberOfRows += 1
let url = result.stringForColumnIndex(0)
urls.append(url)
print("\(url), \(i)")
}
}
print(numberOfRows)