URL Loading System Programming Guide - Apple Developer

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About the URL Loading System At a Glance Relevant Chapter: “Authentication Challenges and TLS Chain Validation” (page 53) Cache Management The URL loading system provides a composite on-disk and in-memory cache allowing an app to reduce its dependence on a network connection and provide faster turnaround for previously cached responses. The cache is stored on a per-app basis. The cache is queried by NSURLConnection according to the cache policy specified by the initiating NSURLRequest object. The NSURLCache class provides methods to configure the cache size and its location on disk. It also provides methods to manage the collection of NSCachedURLResponse objects that contain the cached responses. An NSCachedURLResponse object encapsulates the NSURLResponse object and the URL content data. NSCachedURLResponse also provides a user info dictionary that your app can use to cache any custom data. Not all protocol implementations support response caching. Currently only http and https requests are cached. An NSURLConnection object can control whether a response is cached and whether the response should be cached only in memory by implementing the connection:willCacheResponse:delegate method. Relevant Chapter: “Understanding Cache Access” (page 58) Cookie Storage Due to the stateless nature of the HTTP protocol, clients often use cookies to provide persistent storage of data across URL requests. The URL loading system provides interfaces to create and manage cookies, to send cookies as part of an HTTP request, and to receive cookies when interpreting a web server’s response. OS X and iOS provide the NSHTTPCookieStorage class, which in turn provides the interface for managing a collection of NSHTTPCookie objects. In OS X, cookie storage is shared across all apps; in iOS, cookie storage is per-app. Relevant Chapter: “Cookie Storage” (page 62) Protocol Support The URL loading system natively supports the http, https, file, ftp, and data protocols. However, the URL loading system also allows your app to register your own classes to support additional application-layer networking protocols. You can also add protocol-specific properties to URL request and URL response objects. 2013-10-22 | Copyright © 2003, 2013 Apple Inc. All Rights Reserved. 12
About the URL Loading System How to Use This Document Relevant Chapter: “Cookies and Custom Protocols” (page 62) How to Use This Document This document is largely divided based on which URL loading class the chapter describes. To decide which API to use, read “URL Loading” (page 8). After you decide which API you want to use, read the appropriate API-specific chapter or chapters: ● ● ● For using the NSURLSession class to asynchronously fetch the contents of a URL to memory or download files to disk, read “Using NSURLSession” (page 15). Then read “Life Cycle of a URL Session” (page 64) to learn in detail how NSURLSession interacts with its delegates. For using NSURLConnection to asynchronously fetch the contents of a URL to memory, read “Using NSURLConnection” (page 32). For using NSURLDownload to download files asynchronously to disk, read “Using NSURLDownload” (page 40). After reading one or more of these API-specific chapters, you should also read the following chapters, which are relevant to all three APIs: ● ● ● ● ● “Encoding URL Data” (page 48) explains how to encode arbitrary strings to make them safe for use in a URL. “Handling Redirects and Other Request Changes” (page 50) describes the options you have for responding to a change to your URL request. “Authentication Challenges and TLS Chain Validation” (page 53) describes the process for authenticating your connection against a secure server. “Understanding Cache Access” (page 58) describes how a connection uses the cache during a request. “Cookies and Custom Protocols” (page 62) explains the classes available for managing cookie storage and supporting custom application-layer protocols. See Also The following sample code is available: ● LinkedImageFetcher (OS X) and AdvancedURLConnections (iOS) use NSURLConnection with custom authentication. 2013-10-22 | Copyright © 2003, 2013 Apple Inc. All Rights Reserved. 13
Page 1 and 2: URL Loading System Programming Guid
Page 3 and 4: Contents Making a POST Request 36 R
Page 5 and 6: Listings Understanding Cache Access
Page 7 and 8: About the URL Loading System At a G
Page 9 and 10: About the URL Loading System At a G
Page 11: About the URL Loading System At a G
Page 15 and 16: Using NSURLSession The NSURLSession
Page 17 and 18: Using NSURLSession Understanding UR
Page 19 and 20: Using NSURLSession Creating and Con
Page 21 and 22: Using NSURLSession Creating and Con
Page 23 and 24: Using NSURLSession Fetching Data Us
Page 25 and 26: Using NSURLSession Downloading File
Page 27 and 28: Using NSURLSession Uploading Body C
Page 29 and 30: Using NSURLSession Handling iOS Bac
Page 31 and 32: Using NSURLSession Handling iOS Bac
Page 33 and 34: Using NSURLConnection Creating a Co
Page 35 and 36: Using NSURLConnection Creating a Co
Page 37 and 38: Using NSURLConnection Making a POST
Page 39 and 40: Using NSURLConnection Retrieving Da
Page 41 and 42: Using NSURLDownload Downloading to
Page 43 and 44: Using NSURLDownload Downloading a F
Page 45 and 46: Using NSURLDownload Displaying Down
Page 47 and 48: Using NSURLDownload Decoding Encode
Page 49 and 50: Encoding URL Data CFStringRef decod
Page 51 and 52: Handling Redirects and Other Reques
Page 53 and 54: Authentication Challenges and TLS C
Page 59 and 60: Understanding Cache Access Cache Us
Page 61 and 62: Understanding Cache Access Controll
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Cookies and Custom Protocols Protoc
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Life Cycle of a URL Session Life Cy
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Document Revision History Date 2003
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URL Loading System Programming Guide - Apple Developer

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