swift 单例实现

swift 单例实现

static var onceToken:dispatch_once_t = 0
static var instance : NetworkTools?

class func shareTools() -> NetworkTools {

dispatch_once(&onceToken) { () -> Void in
instance = NetworkTools()
}

return instance!
}

internal required init(){
super.init()
}

static let _instance : NetworkTools = {

let tool  = NetworkTools()
//tool.responseSerializer = AFHTTPResponseSerializer()
tool.responseSerializer.acceptableContentTypes?.insert("text/plain")
return tool
}()