//: Playground - noun: a place where people can playimport UIKitvar dict = [1:"one", 2:"two", 3:"three", 4:"four"]dict.countdict.isEmptydict[1]dict[66]"课程名称: " + dict[1]!// 添加和修改dict[5] = "five"dict[4] = "44444"dict.updateValue("2222", forKey: 2);dict// 删除dict[1] = nil;dict.removeValueForKey(5)dict// 遍历for (key, value) in dict {    print("key:\(key) value:\(value)")}dict.keysdict.valuesfor key in dict.keys {    print(key)}for value in dict.values {    print(value)}