最近AFNetWorking的2.X和3.X的源码之后，决定看一下Amalofire网路库的实现，现在最新版本是4.5.0版本.主要代码结构如图所示:
Alamofire.png
文件太多，不太好在一篇文章中阐述，先从AFError和Notification开始吧.
AFError
如果对Swift中的枚举不熟悉，看AFError会感觉有点陌生，AFError将错误分为四大类型，每个类型继续进行枚举:
public enum AFError: Error {
public enum ParameterEncodingFailureReason {
case missingURL
case jsonEncodingFailed(error: Error)
case propertyListEncodingFailed(error: Error)
}
public enum MultipartEncodingFailureReason {
case bodyPartURLInvalid(url: URL)
case bodyPartFilenameInvalid(in: URL)
case bodyPartFileNotReachable(at: URL)
case bodyPartFileNotReachableWithError(atURL: URL, error: Error)
case bodyPartFileIsDirectory(at: URL)
case bodyPartFileSizeNotAvailable(at: URL)
case bodyPartFileSizeQueryFailedWithError(forURL: URL, error: Error)
case bodyPartInputStreamCreationFailed(for: URL)
case outputStreamCreationFailed(for: URL)
case outputStreamFileAlreadyExists(at: URL)
case outputStreamURLInvalid(url: URL)
case outputStreamWriteFailed(error: Error)
case inputStreamReadFailed(error: Error)
}
/// The underlying reason the response validation error occurred.
///
/// - dataFileNil: The data file containing the server response did not exist.
/// - dataFileReadFailed: The data file containing the server response could not be read.
/// - missingContentType: The response did not contain a `Content-Type` and the `acceptableContentTypes`
/// provided did not contain wildcard type.
/// - unacceptableContentType: The response `Content-Type` did not match any type in the provided
/// `acceptableContentTypes`.
/// - unacceptableStatusCode: The response status code was not acceptable.
public enum ResponseValidationFailureReason {
case dataFileNil
case dataFileReadFailed(at: URL)
case missingContentType(acceptableContentTypes: [String])
case unacceptableContentType(acceptableContentTypes: [String], responseContentType: String)
case unacceptableStatusCode(code: Int)
}
/// The underlying reason the response serialization error occurred.
///
/// - inputDataNil: The server response contained no data.
/// - inputDataNilOrZeroLength: The server response contained no data or the data was zero length.
/// - inputFileNil: The file containing the server response did not exist.
/// - inputFileReadFailed: The file containing the server response could not be read.
/// - stringSerializationFailed: String serialization failed using the provided `String.Encoding`.
/// - jsonSerializationFailed: JSON serialization failed with an underlying system error.
/// - propertyListSerializationFailed: Property list serialization failed with an underlying system error.
public enum ResponseSerializationFailureReason {
case inputDataNil
case inputDataNilOrZeroLength
case inputFileNil
case inputFileReadFailed(at: URL)
case stringSerializationFailed(encoding: String.Encoding)
case jsonSerializationFailed(error: Error)
case propertyListSerializationFailed(error: Error)
}
case invalidURL(url: URLConvertible)
case parameterEncodingFailed(reason: ParameterEncodingFailureReason)
case multipartEncodingFailed(reason: MultipartEncodingFailureReason)
case responseValidationFailed(reason: ResponseValidationFailureReason)
case responseSerializationFailed(reason: ResponseSerializationFailureReason)
}
我们最熟悉的枚举定义是这样的:
enum NetError {
case notReachable
case reachable
}
调用也比较简单:
var netError:NetError = NetError.notReachable
switch netError {
case .notReachable:
print("无网")
case .reachable:
print("无网")
}`</code></pre>
Swift中枚举有一个重要的特性是关连值枚举，以图形为例的枚举如下:
<pre><code>`enum Shape {
case Rectangle(CGRect)
case Circle(CGPoint,Int)
}
枚举使用如下:
var rect = Shape.Rectangle(CGRect(x: 0, y: 0, width: 100, height: 100))
var circle = Shape.Circle(CGPoint(x: 50, y: 50),50)
switch(rect) {
case .Rectangle(let rect):
print("矩形位置:\(rect)")
case let .Circle(center, radius):
print("圆心:\(center)--半径:\(radius)")
}
if case let Shape.Rectangle(rect) = rect {
print("矩形位置:\(rect)")
}
if case let Shape.Circle(center, radius) = rect {
print("圆心:\(center)--半径:\(radius)")
}
AFError在编码的时候作为异常抛出的使用:
public func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest {
var urlRequest = try urlRequest.asURLRequest()
guard let parameters = parameters else { return urlRequest }
do {
let data = try JSONSerialization.data(withJSONObject: parameters, options: options)
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
}
AFError对包含的枚举和自身错误描述都做了扩展:
extension AFError: LocalizedError {
public var errorDescription: String? {
switch self {
case .invalidURL(let url):
return "URL is not valid: \(url)"
case .parameterEncodingFailed(let reason):
return reason.localizedDescription
case .multipartEncodingFailed(let reason):
return reason.localizedDescription
case .responseValidationFailed(let reason):
return reason.localizedDescription
case .responseSerializationFailed(let reason):
return reason.localizedDescription
}
}
}
extension AFError.ParameterEncodingFailureReason {
var localizedDescription: String {
switch self {
case .missingURL:
return "URL request to encode was missing a URL"
case .jsonEncodingFailed(let error):
return "JSON could not be encoded because of error:\n\(error.localizedDescription)"
case .propertyListEncodingFailed(let error):
return "PropertyList could not be encoded because of error:\n\(error.localizedDescription)"
}
}
}
Notification
Notification整个文件的代码扩展了Notification添加了Key结构体，定义了通知的类型状态，继续，完成，取消和暂停.
extension Notification.Name {
/// Used as a namespace for all `URLSessionTask` related notifications.
public struct Task {
/// Posted when a `URLSessionTask` is resumed. The notification `object` contains the resumed `URLSessionTask`.
public static let DidResume = Notification.Name(rawValue: "org.alamofire.notification.name.task.didResume")
/// Posted when a `URLSessionTask` is suspended. The notification `object` contains the suspended `URLSessionTask`.
public static let DidSuspend = Notification.Name(rawValue: "org.alamofire.notification.name.task.didSuspend")
/// Posted when a `URLSessionTask` is cancelled. The notification `object` contains the cancelled `URLSessionTask`.
public static let DidCancel = Notification.Name(rawValue: "org.alamofire.notification.name.task.didCancel")
/// Posted when a `URLSessionTask` is completed. The notification `object` contains the completed `URLSessionTask`.
public static let DidComplete = Notification.Name(rawValue: "org.alamofire.notification.name.task.didComplete")
}
}
// MARK: -
extension Notification {
/// Used as a namespace for all `Notification` user info dictionary keys.
public struct Key {
/// User info dictionary key representing the `URLSessionTask` associated with the notification.
public static let Task = "org.alamofire.notification.key.task"
}
}
Alamofire实际调用过程如下:
open func resume() {
guard let task = task else { delegate.queue.isSuspended = false ; return }
if startTime == nil { startTime = CFAbsoluteTimeGetCurrent() }
task.resume()
NotificationCenter.default.post(
name: Notification.Name.Task.DidResume,
object: self,
userInfo: [Notification.Key.Task: task]
)
}
/// Suspends the request.
open func suspend() {
guard let task = task else { return }
task.suspend()
NotificationCenter.default.post(
name: Notification.Name.Task.DidSuspend,
object: self,
userInfo: [Notification.Key.Task: task]
)
}
/// Cancels the request.
open func cancel() {
guard let task = task else { return }
task.cancel()
NotificationCenter.default.post(
name: Notification.Name.Task.DidCancel,
object: self,
userInfo: [Notification.Key.Task: task]
)
}
ParameterEncoding
ParameterEncoding比较好理解就是参数编码，Http请求的八种方法:
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"
}
ParameterEncoding是一个协议，定义了一个Encode方法:
public protocol ParameterEncoding {
/// Creates a URL request by encoding parameters and applying them onto an existing request.
///
/// - parameter urlRequest: The request to have parameters applied.
/// - parameter parameters: The parameters to apply.
///
/// - throws: An `AFError.parameterEncodingFailed` error if encoding fails.
///
/// - returns: The encoded request.
func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest
}
URLEncoding的实现encode过程:
public func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest {
var urlRequest = try urlRequest.asURLRequest()
guard let parameters = parameters else { return urlRequest }
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 { $0 + "&" } ?? "") + query(parameters)
urlComponents.percentEncodedQuery = percentEncodedQuery
urlRequest.url = urlComponents.url
}
} else {
if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
urlRequest.setValue("application/x-www-form-urlencoded; charset=utf-8", forHTTPHeaderField: "Content-Type")
}
urlRequest.httpBody = query(parameters).data(using: .utf8, allowLossyConversion: false)
}
return urlRequest
}
Swift中的百分比编码，8.3系统提供了简单的处理方式:
public func escape(_ string: String) -> String {
let generalDelimitersToEncode = ":#[]@" // does not include "?" or "/" due to RFC 3986 - Section 3.4
let subDelimitersToEncode = "!$&'()*+,;="
var allowedCharacterSet = CharacterSet.urlQueryAllowed
allowedCharacterSet.remove(charactersIn: "\(generalDelimitersToEncode)\(subDelimitersToEncode)")
var escaped = ""
//==========================================================================================================
//
// Batching is required for escaping due to an internal bug in iOS 8.1 and 8.2. Encoding more than a few
// hundred Chinese characters causes various malloc error crashes. To avoid this issue until iOS 8 is no
// longer supported, batching MUST be used for encoding. This introduces roughly a 20% overhead. For more
// info, please refer to:
//
// - 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.substring(with: range)
escaped += substring.addingPercentEncoding(withAllowedCharacters: allowedCharacterSet) ?? substring
index = endIndex
}
}
return escaped
}
JSONEncoding的URLRequest关于Content-Type设置:
if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
urlRequest.setValue("application/json", forHTTPHeaderField: "Content-Type")
}
PropertyListEncoding中URLRequest关于Content-Type的设置:
if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
urlRequest.setValue("application/x-plist", forHTTPHeaderField: "Content-Type")
}
文件末位有个有意思的关于NSNumber是否是Bool类型的扩展:
extension NSNumber {
fileprivate var isBool: Bool { return CFBooleanGetTypeID() == CFGetTypeID(self) }
}
参考资料
Swift 中的枚举，你应该了解的东西
