---
title: "connection(_:willCacheResponse:)"
framework: foundation
role: symbol
role_heading: Instance Method
path: "foundation/nsurlconnectiondatadelegate/connection(_:willcacheresponse:)"
---

# connection(_:willCacheResponse:)

Sent before the connection stores a cached response in the cache, to give the delegate an opportunity to alter it.

## Declaration

```swift
optional func connection(_ connection: NSURLConnection, willCacheResponse cachedResponse: CachedURLResponse) -> CachedURLResponse?
```

## Parameters

- `connection`: The connection sending the message.
- `cachedResponse`: The proposed cached response to store in the cache.

## Return Value

Return Value The actual cached response to store in the cache. The delegate may return cachedResponse unmodified, return a modified cached response, or return nil if no cached response should be stored for the connection.

## Discussion

Discussion This method is called only if the URLProtocol handling the request decides to cache the response. As a rule, responses are cached only when all of the following are true: The request is for an HTTP or HTTPS URL (or your own custom networking protocol that supports caching). The request was successful (with a status code in the 200–299 range). The provided response came from the server, rather than out of the cache. The NSURLRequest object’s cache policy allows caching. The cache-related headers in the server’s response (if present) allow caching. The response size is small enough to reasonably fit within the cache. (For example, if you provide a disk cache, the response must be no larger than about 5% of the disk cache size.)