iOS 使用 NSURLConnection 的 Cache 突然某一天開始，成效驚人，完全不會來問 ETag，也不來問 Server，直到過期為止，完全不來碰 Server，所以研究看看他是看哪個 Header、要怎麼不讓他 Cache 等等的資料。
iOS 使用 NSURLConnection 的 Cache 注意事項
NSURLConnection 主要看 "Cache-Control" and "Expires"，若要不被 Cache：
- Expires：設定為現在日期時間，範例格式：expires: Mon, 26 Feb 2018 01:50:04 GMT
- Cache-Control: max-age=0
- Apple 官方文件：Understanding Cache Access
下述摘錄自此篇：Preventing NSURLConnection Cache Issues
- NSURLRequestUseProtocolCachePolicy: This is the default value and means that depending on what the protocol dictates, the best fitting policy will be used.
- You can use the "Cache-Control" and "Expires" header values that the server returns to control how iOS will cache the data.
- For example, if you don’t want it to cache at all, you can set the "Expires" date equal to the Date header value and "Cache-Control: max-age=0".
相關網頁
- Technical Q&A QA1727: TLS Session Cache
- This solution can better be achieved by adopting the NSURLSession API.
- Using this framework, you can created two NSURLSessions, one for each desired connection.
- Since NSURLSession maintains it's own TLS session cache, the second connection will avoid consulting the first cache, and will return the authentication challenge
- HTTP/1.1: Header Field Definitions
