这个文件里面写了三种参数编码的方式：URLEncoding、JSONEncoding和PropertyListEncoding。
1. 辅助类型
// 用枚举列举了请求方法，并且用大写的形式指定了rawValue
public enum HTTPMethod: String {
case options = "OPTIONS"
case get = "GET"
case head = "HEAD"
case post = "POST"
case put = "PUT"
case patch = "PATCH"
case delete = "DELETE"
case trace = "TRACE"
case connect = "CONNECT"
}
// Dictionary类型的参数
public typealias Parameters = [String: Any]
2. ParameterEncoding协议
规定了如何把参数编码到请求当中。
public protocol ParameterEncoding {
func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest
}
3. URLEncoding
把参数直接编码到URL中。
1). Destination
列举了参数编码到请求中的三种方式。
// methodDependent: 由请求方法自己决定，`GET`, `HEAD` 和 `DELETE`直接拼接到请求url中，其他方法放到HTTP body
// queryString: 直接拼接到请求url中
// httpBody: 放到HTTP body
public enum Destination {
case methodDependent, queryString, httpBody
}
2). 属性和初始化
// 编码方式是methodDependent的URLEncoding实例
public static var `default`: URLEncoding { return URLEncoding() }
// 编码方式是methodDependent的URLEncoding实例，其实跟default是相同的
public static var methodDependent: URLEncoding { return URLEncoding() }
// 编码方式是queryString的URLEncoding实例
public static var queryString: URLEncoding { return URLEncoding(destination: .queryString) }
// 编码方式是httpBody的URLEncoding实例
public static var httpBody: URLEncoding { return URLEncoding(destination: .httpBody) }
public let destination: Destination
public init(destination: Destination = .methodDependent) {
self.destination = destination
}
3). 编码
// 实现ParameterEncoding协议
public func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest {
var urlRequest = try urlRequest.asURLRequest()
// 如果没有传入参数，直接返回
guard let parameters = parameters else { return urlRequest }
// 把参数编码到URL中
if let method = HTTPMethod(rawValue: urlRequest.httpMethod ?? "GET"), encodesParametersInURL(with: method) {
guard let url = urlRequest.url else {
throw AFError.parameterEncodingFailed(reason: .missingURL)
}
if var urlComponents = URLComponents(url: url, resolvingAgainstBaseURL: false), !parameters.isEmpty {
let percentEncodedQuery = (urlComponents.percentEncodedQuery.map { $0 + "&" } ?? "") + query(parameters)
urlComponents.percentEncodedQuery = percentEncodedQuery
urlRequest.url = urlComponents.url
}
} else { // 把参数编码到HTTP body
if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
urlRequest.setValue("application/x-www-form-urlencoded; charset=utf-8", forHTTPHeaderField: "Content-Type")
}
urlRequest.httpBody = query(parameters).data(using: .utf8, allowLossyConversion: false)
}
return urlRequest
}
// 根据传入的key和value，返回处理好的查询字符串组件
public func queryComponents(fromKey key: String, value: Any) -> [(String, String)] {
var components: [(String, String)] = []
if let dictionary = value as? [String: Any] { // value是字典
for (nestedKey, value) in dictionary {
// 用递归再次处理key和value
components += queryComponents(fromKey: "\(key)[\(nestedKey)]", value: value)
}
} else if let array = value as? [Any] { // value是数组
for value in array {
// 用递归再次处理key和value
components += queryComponents(fromKey: "\(key)[]", value: value)
}
} else if let value = value as? NSNumber { // value是NSNumber
if value.isBool {
// NSNumber其实是Bool类型，用1或者0代替
components.append((escape(key), escape((value.boolValue ? "1" : "0"))))
} else {
components.append((escape(key), escape("\(value)")))
}
} else if let bool = value as? Bool { // value是Bool类型，用1或者0代替
components.append((escape(key), escape((bool ? "1" : "0"))))
} else {
components.append((escape(key), escape("\(value)")))
}
return components
}
// 对字符串进行百分号编码。
// 下面这些分隔符保留原字符串：
// - General Delimiters: ":", "#", "[", "]", "@"
// - Sub-Delimiters: "!", "$", "&", "'", "(", ")", "*", "+", ",", ";", "="
public func escape(_ string: String) -> String {
let generalDelimitersToEncode = ":#[]@"
let subDelimitersToEncode = "!$&'()*+,;="
var allowedCharacterSet = CharacterSet.urlQueryAllowed
allowedCharacterSet.remove(charactersIn: "\(generalDelimitersToEncode)\(subDelimitersToEncode)")
var escaped = ""
//==========================================================================================================
//
// 在iOS 8.1和8.2中，如果一次性对大量的中文字符进行百分号编码会造成crash，所以进行了分批处理
// （这个bug是国人发现的，具体可以查看这个issue：https://github.com/Alamofire/Alamofire/issues/206）
//
//==========================================================================================================
if #available(iOS 8.3, *) {
escaped = string.addingPercentEncoding(withAllowedCharacters: allowedCharacterSet) ?? string
} else {
let batchSize = 50
var index = string.startIndex
while index != string.endIndex {
let startIndex = index
let endIndex = string.index(index, offsetBy: batchSize, limitedBy: string.endIndex) ?? string.endIndex
let range = startIndex..<endIndex
let substring = string[range]
escaped += substring.addingPercentEncoding(withAllowedCharacters: allowedCharacterSet) ?? String(substring)
index = endIndex
}
}
return escaped
}
// 返回一个进行了百分号编码并且拼接好的字符串
private func query(_ parameters: [String: Any]) -> String {
var components: [(String, String)] = []
// `<`这个其实是一个其实是一个closure，意思是让keys按照从小到大的顺序重新排列
for key in parameters.keys.sorted(by: <) {
let value = parameters[key]!
components += queryComponents(fromKey: key, value: value)
}
return components.map { "\($0)=\($1)" }.joined(separator: "&")
}
// 判断是否要把参数编码到URL里
private func encodesParametersInURL(with method: HTTPMethod) -> Bool {
switch destination {
case .queryString:
return true
case .httpBody:
return false
default:
break
}
switch method {
case .get, .head, .delete:
return true
default:
return false
}
}
4. JSONEncoding
把参数以SJON类型编码到请求体中。
1). 属性和初始化
// 默认的JSONEncoding实例
public static var `default`: JSONEncoding { return JSONEncoding() }
// 用更好输出效果的JSONEncoding实例
public static var prettyPrinted: JSONEncoding { return JSONEncoding(options: .prettyPrinted) }
public let options: JSONSerialization.WritingOptions
public init(options: JSONSerialization.WritingOptions = []) {
self.options = options
}
2). 编码
// 把字典编码到请求体中
public func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest {
var urlRequest = try urlRequest.asURLRequest()
// 没有参数，直接返回
guard let parameters = parameters else { return urlRequest }
do {
// 把参数序列化成JSON
let data = try JSONSerialization.data(withJSONObject: parameters, options: options)
// 设置Content-Type
if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
urlRequest.setValue("application/json", forHTTPHeaderField: "Content-Type")
}
urlRequest.httpBody = data
} catch {
throw AFError.parameterEncodingFailed(reason: .jsonEncodingFailed(error: error))
}
return urlRequest
}
// 其实根上面那个方法几乎一样，只是第二个参数类型不同
public func encode(_ urlRequest: URLRequestConvertible, withJSONObject jsonObject: Any? = nil) throws -> URLRequest {
var urlRequest = try urlRequest.asURLRequest()
guard let jsonObject = jsonObject else { return urlRequest }
do {
// 把参数序列化成JSON
let data = try JSONSerialization.data(withJSONObject: jsonObject, options: options)
// 设置Content-Type
if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
urlRequest.setValue("application/json", forHTTPHeaderField: "Content-Type")
}
urlRequest.httpBody = data
} catch {
throw AFError.parameterEncodingFailed(reason: .jsonEncodingFailed(error: error))
}
return urlRequest
}
5. PropertyListEncoding
把参数以PropertyList类型编码到请求体中。
1). 属性和初始化
// 默认的PropertyListEncoding实例，以xml的形式序列化
public static var `default`: PropertyListEncoding { return PropertyListEncoding() }
// 以xm的形式序列化的PropertyListEncoding实例
public static var xml: PropertyListEncoding { return PropertyListEncoding(format: .xml) }
// 以二进制的形式序列化的PropertyListEncoding实例
public static var binary: PropertyListEncoding { return PropertyListEncoding(format: .binary) }
public let format: PropertyListSerialization.PropertyListFormat
public let options: PropertyListSerialization.WriteOptions
public init(
format: PropertyListSerialization.PropertyListFormat = .xml,
options: PropertyListSerialization.WriteOptions = 0)
{
self.format = format
self.options = options
}
2). 编码
// 实现ParameterEncoding协议
public func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest {
var urlRequest = try urlRequest.asURLRequest()
guard let parameters = parameters else { return urlRequest }
do {
// 把参数序列化成PropertyList
let data = try PropertyListSerialization.data(
fromPropertyList: parameters,
format: format,
options: options
)
// 设置Content-Type
if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
urlRequest.setValue("application/x-plist", forHTTPHeaderField: "Content-Type")
}
urlRequest.httpBody = data
} catch {
throw AFError.parameterEncodingFailed(reason: .propertyListEncodingFailed(error: error))
}
return urlRequest
}
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