一. 首先看一下request用法
SessionManager.default.request(urlString, method: .get, parameters: nil, encoding: URLEncoding.default).response { (response) in
debugPrint(response)
}
二. 详细参数解析
open func request(
_ url: URLConvertible,
method: HTTPMethod = .get,
parameters: Parameters? = nil,
encoding: ParameterEncoding = URLEncoding.default,
headers: HTTPHeaders? = nil)
-> DataRequest
{
var originalRequest: URLRequest?
do {
originalRequest = try URLRequest(url: url, method: method, headers: headers)
let encodedURLRequest = try encoding.encode(originalRequest!, with: parameters)
return request(encodedURLRequest)
} catch {
return request(originalRequest, failedWith: error)
}
}
-
url : URLConvertible,针对入参有三种处理方式：
是
String，转换成URL后返回
是URL，直接使用
是URLComponents，直接返回
//传入`String `,转为`URL`
extension String: URLConvertible {
public func asURL() throws -> URL {
guard let url = URL(string: self) else { throw AFError.invalidURL(url: self) }
return url
}
}
//如果传入的是`URL `,直接返回
extension URL: URLConvertible {
public func asURL() throws -> URL { return self }
}
extension URLComponents: URLConvertible {
public func asURL() throws -> URL {
guard let url = url else { throw AFError.invalidURL(url: self) }
return url
}
}
-
method默认是get,支持以下几种
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"
}
-
parameters传进来的参数
public typealias Parameters = [String: Any]
-
encoding编码格式，默认URLEncoding.default,有以下几种格式：
URLEncoding
JSONEncoding
PropertyListEncoding
-
headers请求头信息，默认nil
public typealias HTTPHeaders = [String: String]
- 返回
DataRequest
三. 源码分析
1. 编码
- 首先初始化一个
originalRequest
originalRequest = try URLRequest(url: url, method: method, headers: headers)
- 编码后返回
request(encodedURLRequest)
let encodedURLRequest = try encoding.encode(originalRequest!, with: parameters)
return request(encodedURLRequest)
-
encode编码，通过下面源码可以看到，最后都会处理参数query，主要分两种情况
encodesParametersInURL如果是.get, .head, .delete三种方式，进行百分号编码，放入到percentEncodedQuery中- 其他的请求方式，设置
header,然后将参数拼接到请求体httpbody中
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
}
-
query遍历参数
private func query(_ parameters: [String: Any]) -> String {
var components: [(String, String)] = []
for key in parameters.keys.sorted(by: <) {
let value = parameters[key]!
components += queryComponents(fromKey: key, value: value)
}
return components.map { "\($0)=\($1)" }.joined(separator: "&")
}
- 通过
ASCII排序 -
queryComponents对参数进行递归，进行编码处理后，以元组形式保存在components中返回，
public func queryComponents(fromKey key: String, value: Any) -> [(String, String)] {
var components: [(String, String)] = []
if let dictionary = value as? [String: Any] {
for (nestedKey, value) in dictionary {
components += queryComponents(fromKey: "\(key)[\(nestedKey)]", value: value)
}
} else if let array = value as? [Any] {
for value in array {
components += queryComponents(fromKey: arrayEncoding.encode(key: key), value: value)
}
} else if let value = value as? NSNumber {
if value.isBool {
components.append((escape(key), escape(boolEncoding.encode(value: value.boolValue))))
} else {
components.append((escape(key), escape("\(value)")))
}
} else if let bool = value as? Bool {
components.append((escape(key), escape(boolEncoding.encode(value: bool))))
} else {
components.append((escape(key), escape("\(value)")))
}
return components
}
-
components.map { "\($0)=\($1)" }.joined(separator: "&")将参数之间插入&符号
2. request内部逻辑解剖：
open func request(_ urlRequest: URLRequestConvertible) -> DataRequest {
var originalRequest: URLRequest?
do {
originalRequest = try urlRequest.asURLRequest()
let originalTask = DataRequest.Requestable(urlRequest: originalRequest!)
let task = try originalTask.task(session: session, adapter: adapter, queue: queue)
let request = DataRequest(session: session, requestTask: .data(originalTask, task))
delegate[task] = request
if startRequestsImmediately { request.resume() }
return request
} catch {
return request(originalRequest, failedWith: error)
}
}
2.1 创建Task
let originalTask = DataRequest.Requestable(urlRequest: originalRequest!)
借助DataRequest内部的结构体Requestable创建Task
通过
urlRequest初始化Requestable
然后再用originalTask创建Task
返回queue.sync { session.dataTask(with: urlRequest) }
struct Requestable: TaskConvertible {
let urlRequest: URLRequest
func task(session: URLSession, adapter: RequestAdapter?, queue: DispatchQueue) throws -> URLSessionTask {
do {
let urlRequest = try self.urlRequest.adapt(using: adapter)
return queue.sync { session.dataTask(with: urlRequest) }
} catch {
throw AdaptError(error: error)
}
}
}
2.2 创建request:
let request = DataRequest(session: session, requestTask: .data(originalTask, task))
- 调用
DataRequest的父类Request的初始化方法.通过传入枚举的方式，初始化参数同时保存信息，此时传入的是.data(let originalTask, let task)
init(session: URLSession, requestTask: RequestTask, error: Error? = nil) {
self.session = session
switch requestTask {
case .data(let originalTask, let task):
taskDelegate = DataTaskDelegate(task: task)
self.originalTask = originalTask
case .download(let originalTask, let task):
taskDelegate = DownloadTaskDelegate(task: task)
self.originalTask = originalTask
case .upload(let originalTask, let task):
taskDelegate = UploadTaskDelegate(task: task)
self.originalTask = originalTask
case .stream(let originalTask, let task):
taskDelegate = TaskDelegate(task: task)
self.originalTask = originalTask
}
delegate.error = error
delegate.queue.addOperation { self.endTime = CFAbsoluteTimeGetCurrent() }
- 初始化
taskDelegate,调用super.init(task: task)
override init(task: URLSessionTask?) {
mutableData = Data()
progress = Progress(totalUnitCount: 0)
super.init(task: task)
}
- 调用父类初始化方法
init(task: URLSessionTask?)保存_task,初始化队列
init(task: URLSessionTask?) {
_task = task
self.queue = {
let operationQueue = OperationQueue()
operationQueue.maxConcurrentOperationCount = 1
operationQueue.isSuspended = true
operationQueue.qualityOfService = .utility
return operationQueue
}()
}
- 保存
self.originalTask = originalTask
2.3 保存request:
delegate[task] = request，将request保存到SessionDelegate中，便于SessionDelegate管理
open subscript(task: URLSessionTask) -> Request? {
get {
lock.lock() ; defer { lock.unlock() }
return requests[task.taskIdentifier]
}
set {
lock.lock() ; defer { lock.unlock() }
requests[task.taskIdentifier] = newValue
}
}
2.4 启动request.resume()
if startRequestsImmediately { request.resume() }
以上就是request启动流程，通过上面流程分析，可知：
SessionDelegate是总的任务管理者，具体执行的时候，通过不同的request如：DataRequest,DownloadRequest,UploadRequest等去处理，实现解耦的目的。
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