下面是一个简单的代码式例：

/// Objective-C
/// CDSessionDelegate.h
#import <Foundation/Foundation.h>
typedef void(^completionHandler)(void);
@interface CDSessionDelegate : NSObject<NSURLSessionDelegate,NSURLSessionTaskDelegate,NSURLSessionDataDelegate,NSURLSessionDownloadDelegate,NSURLSessionStreamDelegate>
@property(nonatomic, strong) NSMutableDictionary <NSString*, completionHandler> *completionHandlers;
@end

/// Swift
/// CDSessionDelegate.swift
import Foundation
typealias CompletionHandler = () -> Void
class CDSessionDelegate: NSObject, URLSessionDelegate, URLSessionTaskDelegate, URLSessionDownloadDelegate, URLSessionDataDelegate, URLSessionStreamDelegate{
    var completionHandlers:[String:CompletionHandler] = [:]
}