The max-stale option can be present with no value, or be present with a number of seconds. By using a struct you can check the nullability of the maxStale variable as well as then check the nullability of the seconds to differentiate.
struct MaxStales8NIOHTTP111HTTPHeadersV5VaporE12CacheControlV8MaxStaleV What are these?80VVMimport NIOHTTP1import VaporVapor is a framework for building server applications, APIs and websites in Swift. It provides a safe, performant and scalable foundation for building large complex backends.
struct CacheControlRepresents the HTTP Cache-Control header.
struct HTTPHeadersA representation of a block of HTTP header fields.
init(mustRevalidated: Bool = false, noCache: Bool = false, noStore: Bool = false, noTransform: Bool = false, isPublic: Bool = false, isPrivate: Bool = false, proxyRevalidate: Bool = false, onlyIfCached: Bool = false, immutable: Bool = false, maxAge: Int? = nil, sMaxAge: Int? = nil, maxStale: MaxStale? = nil, minFresh: Int? = nil, staleWhileRevalidate: Int? = nil, staleIfError: Int? = nil) Creates a new CacheControl.
static func parse(_ value: String) -> CacheControl? var immutable: BoolIndicates that the response body will not change over time.
var isPrivate: BoolThe response is for a single user and must not be stored by a shared cache. A private cache (like the user’s browser cache) may store the response.
var isPublic: BoolThe response may be cached by any cache, even if the response is normally non-cacheable
var maxAge: Int?The maximum amount of time a resource is considered fresh. Unlike theExpires header, this directive is relative to the time of the request.
var maxStale: MaxStale?Indicates the client will accept a stale response. An optional value in seconds indicates the upper limit of staleness the client will accept.
var minFresh: Int?Indicates the client wants a response that will still be fresh for at least the specified number of seconds.
var mustRevalidate: BoolIndicates that once a resource becomes stale, caches must not use their stale copy without successful validation on the origin server.
var noCache: BoolCaches must check with the origin server for validation before using the cached copy.
var noStore: BoolThe cache should not store anything about the client request or server response.
var noTransform: BoolNo transformations or conversions should be made to the resource. The Content-Encoding, Content-Range, Content-Type headers must not be modified by a proxy. A non-transparent proxy or browser feature such as Google’s Light Mode might, for example, convert between image formats in order to save cache space or to reduce the amount of traffic on a slow link. The no-transform directive disallows this.
var onlyIfCached: BoolIndicates to not retrieve new data. This being the case, the server wishes the client to obtain a response only once and then cache. From this moment the client should keep releasing a cached copy and avoid contacting the origin-server to see if a newer copy exists.
var proxyRevalidate: BoolLike must-revalidate, but only for shared caches (e.g., proxies). Ignored by private caches.
var sMaxAge: Int?Overrides max-age or the Expires header, but only for shared caches (e.g., proxies). Ignored by private caches.
var staleIfError: Int?Indicates the client will accept a stale response if the check for a fresh one fails. The value indicates how many seconds long the client will accept the stale response after the initial expiration.
var staleWhileRevalidate: Int?Indicates the client will accept a stale response, while asynchronously checking in the background for a fresh one. The value indicates how long the client will accept a stale response.
func serialize() -> String Generates the header string for this instance.
protocol Sendablevar seconds: Int?The upper limit of staleness the client will accept.