剛寫swift的時候，用的是Alamofire，使用一段時間后，上網查了下NSURLSession的原理，并結合前人技術博客，就自己寫了個工具類。。。

首先，定義一個網絡請求的枚舉類型，定義枚舉類型，是怕有時候不小心，字符串寫錯了
/**
enum HTTPMethod: String {

case GET = "GET"
case POST = "POST"
case PUT = "PUT"
case DELETE = "DELETE

}

其實我們也可以按照下面的寫法，

 *  不需要把和鍵命相同的值字符串寫出來
 */

enum HTTPMethod: String {

case GET, POST, PUT, DELETE

}

第二步：定義一個 NetworkManager 的結構體

{

let method: HTTPMethod
let url: String
let params: [String: AnyObject]?
let callback: (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void
private(set) var request = NSMutableURLRequest()

雖然結構體不需要寫初始化方法，可是有時我們只初始化部分屬性的話，還是的自己寫一個。。。同時，如果你定義屬性的時候，沒有初始化，只是給屬性指定類型的話，結構體的初始化方法必須包含那個屬性。
如request屬性，我已經在定義的時候給它初始化了，下面結構體的初始化也就不需要了

init(method: HTTPMethod, url: String, params: [String: AnyObject]?, callback: (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void) {
    self.url = url
    self.method = method
    self.params = params
    self.callback = callback
}

然后是創建網絡請求request
/**
創建request
*/

private mutating func buildRequest() {
 var newUrl = url
    if method == .GET, let myParams = params where myParams.count > 0 {
        newUrl += "?" + buildParams(myParams)
    }
    guard let URL = NSURL(string: newUrl) else {
        return
    }
    request = NSMutableURLRequest(URL: URL)
    request.HTTPMethod = method.rawValue
}

創建請求體

/**
創建請求體
*/

private func buildBody() {
    guard method != .GET else {
        return
    }
    guard let myParams = params where
        myParams.count > 0 else {
            return
    }
    request.HTTPBody = buildParams(myParams).dataUsingEncoding(NSUTF8StringEncoding)
}

/**
創建并開啟任務
*/

private func fireTask() {
    let session = NSURLSession.sharedSession()
    session.dataTaskWithRequest(request) { (data, response, error) in
        self.callback(data: data, response: response, error: error)
    }.resume()
}

然后寫一個方法，包含了上面的3歌步驟
/**
一整套流程
*/
mutating func start() {

    buildRequest()
    buildBody()
    fireTask()
}

上面創建request和請求體的方法里從Alamofire里提取了3個方法

/**
 請求參數拼接
 */
func buildParams(parameters: [String: AnyObject]) -> String {
    var components: [(String, String)] = []
    
    for key in parameters.keys.sort(<) {
        let value = parameters[key]!
        components += queryComponents(key, value)
    }
    
    return (components.map { "\($0)=\($1)" } as [String]).joinWithSeparator("&")
}


func queryComponents(key: String, _ value: AnyObject) -> [(String, String)] {
    var components: [(String, String)] = []
    
    if let dictionary = value as? [String: AnyObject] {
        for (nestedKey, value) in dictionary {
            components += queryComponents("\(key)[\(nestedKey)]", value)
        }
    } else if let array = value as? [AnyObject] {
        for value in array {
            components += queryComponents("\(key)[]", value)
        }
    } else {
        components.append((escape(key), escape("\(value)")))
    }
    
    return components
}


func escape(string: String) -> String {
    let generalDelimitersToEncode = ":#[]@" // does not include "?" or "/" due to RFC 3986 - Section 3.4
    let subDelimitersToEncode = "!$&'()*+,;="
    
    let allowedCharacterSet = NSCharacterSet.URLQueryAllowedCharacterSet().mutableCopy() as! NSMutableCharacterSet
    allowedCharacterSet.removeCharactersInString(generalDelimitersToEncode + subDelimitersToEncode)
    
    var escaped = ""
    
    if #available(iOS 8.3, OSX 10.10, *) {
        escaped = string.stringByAddingPercentEncodingWithAllowedCharacters(allowedCharacterSet) ?? string
    } else {
        let batchSize = 50
        var index = string.startIndex
        
        while index != string.endIndex {
            let startIndex = index
            let endIndex = index.advancedBy(batchSize, limit: string.endIndex)
            let range = startIndex..<endIndex
            
            let substring = string.substringWithRange(range)
            
            escaped += substring.stringByAddingPercentEncodingWithAllowedCharacters(allowedCharacterSet) ?? substring
            
            index = endIndex
        }
    }
    
    return escaped
}

至此管理類已經創建完成。下面開始寫具體的get和post請求。

字數太多大家都不愿意看，我把它分成了2篇來寫
http://www.lxweimin.com/p/5c8200e3c09a