继承自：NSObject
遵守协议：NSObject
导入声明：@import Foundation;
适用范围：iOS 2.0 及以后
一、概述（Overview）
一个 NSHTTPCookie 对象代表一个 HTTP cookie。NSHTTPCookie 对象是不可变的，它初始化自一个包含 cookie 属性的字典。
NSHTTPCookie 类支持两种不同的 cookie 版本：
版本 0：这种版本指的是传统的或者老式的 cookie，也就是网景（Netscape）公司定义的最初的那种 cookie 格式。我们遇到的大多数 cookie 都是这种格式。
版本 1：这种版本指的是那些在 RFC 2965，HTTP State Management Mechanism 中定义的 cookie。
二、功能（Tasks）
1.创建 NSHTTPCookie 实例（Create cookie instances）
+ cookiesWithResponseHeaderFields:forURL:
Returns an array of NSHTTPCookie objects corresponding to the provided response header fields for the provided URL.
Declaration
+ (NSArray *)cookiesWithResponseHeaderFields:(NSDictionary *)*headerFields*
forURL:(NSURL *)theURL
Parameters
| 参数 | 含义 |
|---|---|
| headerFields | The header fields used to create the NSHTTPCookie objects. |
| theURL | The URL associated with the created cookies. |
Return Value
The array of created cookies.
Discussion
This method ignores irrelevant header fields in headerFields, allowing dictionaries to contain additional data.
If headerFields does not specify a domain for a given cookie, the cookie is created with a default domain value of the URL.
If headerFields does not specify a path for a given cookie, the cookie is created with a default path value of "/".
Availability
Available in iOS 2.0 and later.
+ cookieWithProperties:
Creates and initializes an NSHTTPCookie object using the provided properties.
Declaration
+ (NSHTTPCookie *)cookieWithProperties:(NSDictionary *)properties
Parameters
| 参数 | 含义 |
|---|---|
| properties | The properties for the new cookie object, expressed as key value pairs. |
Return Value
The newly created cookie object. Returns nil if the provided properties are invalid.
Discussion
To successfully create a cookie, you must provide values for (at least) the NSHTTPCookiePath, NSHTTPCookieName, and NSHTTPCookieValue keys, and either the NSHTTPCookieOriginURL key or the NSHTTPCookieDomain key.
See Constants for more information on the available cookie attribute constants and the constraints imposed on the values in the dictionary.
Availability
Available in iOS 2.0 and later.
See Also
– initWithProperties:
- initWithProperties:
Returns an initialized NSHTTPCookie object using the provided properties.
Declaration
- (instancetype)initWithProperties:(NSDictionary *)properties
Parameters
| 参数 | 含义 |
|---|---|
| properties | The properties for the new cookie object, expressed as key value pairs. |
Return Value
The initialized cookie object. Returns nil if the provided properties are invalid.
Discussion
To successfully create a cookie, you must provide values for (at least) the NSHTTPCookiePath, NSHTTPCookieName, and NSHTTPCookieValue
keys, and either the NSHTTPCookieOriginURL key or the NSHTTPCookieDomain key.
See Constants for more information on the available cookie attribute constants and the constraints imposed on the values in the dictionary.
Availability
Available in iOS 2.0 and later.
See Also
+ cookieWithProperties:
2.将 cookie 转成请求头（Convert cookies to request headers）
+ requestHeaderFieldsWithCookies:
Returns a dictionary of header fields corresponding to a provided array of cookies.
Declaration
+ (NSDictionary) *)requestHeaderFieldsWithCookies:(NSArray *)cookies
Parameters
| 参数 | 含义 |
|---|---|
| cookies | The cookies from which the header fields are created. |
Return Value
The dictionary of header fields created from the provided cookies.
Discussion
To send these headers as part of a URL request to a remote server, create an NSMutableURLRequest object, then call the setAllHTTPHeaderFields: or setValue:forHTTPHeaderField: method to set the provided headers for the request. Finally, initialize and start an NSURLSessionTask, NSURLConnection, or NSURLDownload object based on that request object.
Availability
Available in iOS 2.0 and later.
3.获取 cookie 的属性（Getting cookie properties）
comment Property
The receiver's comment string. (read-only)
Declaration
@property(readonly, copy) NSString *comment
Discussion
The receiver’s comment string or nil if the cookie has no comment. This string is suitable for presentation to the user, explaining the contents and purpose of this cookie.
Availability
Available in iOS 2.0 and later.
commentURL Property
The receiver’s comment URL. (read-only)
Declaration
@property(readonly, copy) NSURL *commentURL
Discussion
The receiver’s comment URL or nil if the cookie has none. This value specifies a URL which is suitable for presentation to the user as a link for further information about this cookie.
Availability
Available in iOS 2.0 and later.
domain Property
The domain of the receiver’s cookie. (read-only)
Declaration
@property(readonly, copy) NSString *domain
Discussion
If the domain does not start with a dot, then the cookie is only sent to the exact host specified by the domain. If the domain does start with a dot, then the cookie is sent to other hosts in that domain as well, subject to certain restrictions. See RFC 2965 for more detail.
Availability
Available in iOS 2.0 and later.
expiresDate Property
The receiver’s expiration date. (read-only)
Declaration
@property(readonly, copy) NSDate *expiresDate
Discussion
The receiver’s expiration date, or nil if there is no specific expiration date such as in the case of “session-only” cookies. The expiration date is the date when the cookie should be deleted.
Availability
Available in iOS 2.0 and later.
HTTPOnly Property
A boolean value that indicates whether the receiver should only be sent to HTTP servers per RFC 2965. (read-only)
Declaration
@property(readonly, getter=isHTTPOnly) BOOL HTTPOnly
Discussion
Returns YES if this cookie should only be sent via HTTP headers, NO otherwise.
Cookies may be marked as HTTP only by a server (or by a javascript). Cookies marked as such must only be sent via HTTP Headers in HTTP requests for URL's that match both the path and domain of the respective cookies.
IMPORTANT
Cookies specified as HTTP only should not be delivered to any javascript applications to prevent cross-site scripting vulnerabilities.
Availability
Available in iOS 2.2 and later.
secure Property
A boolean value that indicates whether this cookie should only be sent over secure channels. (read-only)
Declaration
@property(readonly, getter=isSecure) BOOL secure
Discussion
YES if this cookie should only be sent over secure channels, otherwise NO.
Availability
Available in iOS 2.0 and later.
sessionOnly Property
A boolean value that indicates whether the receiver should be discarded at the end of the session (regardless of expiration date). (read-only)
Declaration
@property(readonly, getter=isSessionOnly) BOOL sessionOnly
Discussion
YES if the receiver should be discarded at the end of the session (regardless of expiration date), otherwise NO.
Availability
Available in iOS 2.0 and later.
name Property
The receiver’s name. (read-only)
Declaration
@property(readonly, copy) NSString *name
Availability
Available in iOS 2.0 and later.
path Property
The receiver’s path. (read-only)
Declaration
@property(readonly, copy) NSString *path
Discussion
The cookie will be sent with requests for this path in the cookie's domain, and all paths that have this prefix. A path of "/" means the cookie will be sent for all URLs in the domain.
Availability
Available in iOS 2.0 and later.
portList Property
The receiver's port list. (read-only)
Declaration
@property(readonly, copy) NSArray *portList
Discussion
The list of ports for the cookie, returned as an array of NSNumber objects containing integers. If the cookie has no port list this method returns nil and the cookie will be sent to any port. Otherwise, the cookie is only sent to ports specified in the port list.
Availability
Available in iOS 2.0 and later.
properties Property
The receiver’s cookie properties. (read-only)
Declaration
@property(readonly, copy) NSDictionary *properties
Discussion
This dictionary can be used with initWithProperties: or cookieWithProperties: to create an equivalent NSHTTPCookie object.
See initWithProperties: for more information on the constraints imposed on the properties dictionary.
Availability
Available in iOS 2.0 and later.
value Property
The receiver’s value. (read-only)
Declaration
@property(readonly, copy) NSString *value
Availability
Available in iOS 2.0 and later.
version Property
The receiver’s version. (read-only)
Declaration
@property(readonly) NSUInteger version
Discussion
The receiver's version. Version 0 maps to “old-style” Netscape cookies. Version 1 maps to RFC 2965 cookies.
Availability
Available in iOS 2.0 and later.
三、常量（Constants）
HTTP Cookie 属性的 key（HTTP Cookie Attribute Keys）
These constants define the supported keys in a cookie attributes dictionary.
Declaration
NSString *NSHTTPCookieComment;
NSString *NSHTTPCookieCommentURL;
NSString *NSHTTPCookieDiscard;
NSString *NSHTTPCookieDomain;
NSString *NSHTTPCookieExpires;
NSString *NSHTTPCookieMaximumAge;
NSString *NSHTTPCookieName;
NSString *NSHTTPCookieOriginURL;
NSString *NSHTTPCookiePath;
NSString *NSHTTPCookiePort;
NSString *NSHTTPCookieSecure;
NSString *NSHTTPCookieValue;
NSString *NSHTTPCookieVersion;
Constants
-
NSHTTPCookieComment
An
NSStringobject containing the comment for the cookie.
Only valid for Version 1 cookies and later.** This cookie attribute is optional.**Available in iOS 2.0 and later.
NSHTTPCookieCommentURL
An NSURL object or NSString object containing the comment URL for the cookie.
Only valid for Version 1 cookies or later.** This cookie attribute is optional.**
Available in iOS 2.0 and later.
- NSHTTPCookieDiscard
An NSString object stating whether the cookie should be discarded at the end of the session.
String value must be either "TRUE" or "FALSE". This cookie attribute is optional. The default is "FALSE", unless this cookie is version 1 or greater and a value for NSHTTPCookieMaximumAge is not specified, in which case it is assumed to be "TRUE".
Available in iOS 2.0 and later.
- NSHTTPCookieDomain
An NSString object containing the domain for the cookie.
If this cookie attribute is missing, the domain is inferred from the value for NSHTTPCookieOriginURL. If you do not specify a value for NSHTTPCookieOriginURL, you must specify a value for NSHTTPCookieDomain.
Available in iOS 2.0 and later.
- NSHTTPCookieExpires
An NSDate object or NSString object specifying the expiration date for the cookie.
This cookie attribute is only used for Version 0 cookies.** This cookie attribute is optional.**
Available in iOS 2.0 and later.
- NSHTTPCookieMaximumAge
An NSString object containing an integer value stating how long in seconds the cookie should be kept, at most.
Only valid for Version 1 cookies and later. Default is "0". This cookie attribute is optional.
Available in iOS 2.0 and later.
- NSHTTPCookieName
An NSString object containing the name of the cookie. This cookie attribute is required.
Available in iOS 2.0 and later.
- NSHTTPCookieOriginURL
An NSURL or NSString object containing the URL that set this cookie.
If you do not provide a value for NSHTTPCookieOriginURL, you must provide a value for NSHTTPCookieDomain.
Available in iOS 2.0 and later.
- NSHTTPCookiePath
An NSString object containing the path for the cookie.
This cookie attribute is required.
Available in iOS 2.0 and later.
- NSHTTPCookiePort
An NSString object containing comma-separated integer values specifying the ports for the cookie.
Only valid for Version 1 cookies or later. The default value is an empty string (""). This cookie attribute is optional.
Available in iOS 2.0 and later.
- NSHTTPCookieSecure
An NSString object indicating that the cookie should be transmitted only over secure channels.
Providing any value for this key indicates that the cookie should remain secure.
Available in iOS 2.0 and later.
- NSHTTPCookieValue
An NSString object containing the value of the cookie.
This cookie attribute is required.
Available in iOS 2.0 and later.
- NSHTTPCookieVersion
An NSString object that specifies the version of the cookie.
Must be either "0" or "1". The default is "0". This cookie attribute is optional.
Available in iOS 2.0 and later.
参考（Reference）：
https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSHTTPCookie_Class/index.html#//apple_ref/occ/cl/NSHTTPCookie
问题（Question）：
1.Cookie 是什么？有哪些属性？百度百科-cookie，Wikipedia-HTTP cookie
2.Cookie 有几种格式？
3.RFC 是什么？百度百科-RFC，Wikipedia-RFC
4.Cookie 和 Session 的区别和联系？