enumeration

问题 Swift enumerations have both associated and raw values. But the use cases of these values is not clear to me. So I would really appreciate if anyone can explain the difference between the associated and raw values, an example would be very helpful. 回答1: Raw values are for when every case in the enumeration is represented by a compile-time-set value. The are akin to constants, i.e. let A = 0 let B = 1 is similar to: enum E: Int { case A // if you don't specify, IntegerLiteralConvertible-based

问题 Swift enumerations have both associated and raw values. But the use cases of these values is not clear to me. So I would really appreciate if anyone can explain the difference between the associated and raw values, an example would be very helpful. 回答1: Raw values are for when every case in the enumeration is represented by a compile-time-set value. The are akin to constants, i.e. let A = 0 let B = 1 is similar to: enum E: Int { case A // if you don't specify, IntegerLiteralConvertible-based

问题 This question already has answers here : Collection was modified; enumeration operation may not execute in ArrayList [duplicate] (9 answers) Closed 6 years ago . I have two collections of strings: CollectionA is a StringCollection property of an object stored in the system, while CollectionB is a List generated at runtime. CollectionA needs to be updated to match CollectionB if there are any differences. So I devised what I expected to be a simple LINQ method to perform the removal. var

问题 I read somewhere about giving enums default values like so: typedef enum { MarketNavigationTypeNone = 0, MarketNavigationTypeHeirachy = 1, MarketNavigationTypeMarket = 2 } MarketNavigationLevelType; .. but i can't remember the value of doing this. If i don't give them default values - and then someone later on reorders the enum - what are the risks? If i always use the enum name and don't even refer to them by their integer value, is there any risks? The only possible problem i can think of

问题 Considering such an enumeration : type TTypeOfData = ( [XmlName('ABC')] todABC, [XmlName('DEF')] todDEF, [XmlName('GHI')] todGHI ); Where XmlName is a custom attribute used to define the serialization string for members of this enumeration. How can I explore the attributes attached to each member of this enumeration ? 回答1: Attributes associated with elements in enumerations are not currently stored in Win32 RTTI data in the executable. RTTI is already responsible for a fair increase in the

问题 In my Python 2.7.2 IDLE interpreter: >>> mylist = [1, 2, 3, 4, 5] >>> for item in mylist: mylist.remove(item) >>> mylist [2, 4] Why? 回答1: It's because when you iterate over a list, python keeps track of the index in the list. Consider the following code instead: for i in range(len(mylist)): if i >= len(mylist): break item = mylist[i] mylist.remove(item) If we track this (which is essentially what python is doing in your code), then we see that when we remove an item in the list, the number to

问题 EDITED QUESTION I'm trying to create a class factory that can generate enumeration-like classes with the following properties: Class is initialized from the list of allowed values (i.e., it's automatically generated!). Class creates one instance of itself for each of the allowed value. Class does not allow the creation of any additional instances once the above step is complete (any attempt to do so results in an exception). Class instances provide a method that, given a value, returns a

问题 I tried to look this up online, but all the WSDL examples seem to not really explain if I should mark things as basetype string in the WSDL or int... Basically, I'm trying to make my WSDL so that I can represent an Enumeration. I have a C# Enum in mind already that I want to match it up to... public enum MyEnum { Item1 = 0, Item2 = 1, Item3 = 2, SpecialItem = 99 } I'm not sure how my WSDL should look... I figure it's one of two, but even then I'm not 100% sure... <wsdl:types> <xsd:schema

问题 Is there some kind of mechanism in SQL Server to allow Enumerated type like functionality? For example, if I have a column Called "UpdateStatus" it usually gets setup with single letter values like so: D X U I This could equate to a lot of things. That leads to confusion. The alternative is to have it be a string column like this: Downloaded Deleted Updated Initialized But that has its own problems. Eventually someone is going to write something like this: where UpdateStatus = 'Initalized'

问题 How would I loop through all the values of a Windows Registry Key using the Python module _winreg. I have code that will do what I want, but it is for the subkeys of the specified registry key. Here Is The Code: from _winreg import * t = OpenKey(HKEY_CURRENT_USER, r"PATH TO KEY", 0, KEY_ALL_ACCESS) try: i = 0 while True: subkey = EnumValue(t, i) print subkey i += 1 except WindowsError: # WindowsError: [Errno 259] No more data is available pass Oh, figured it out. But, if anyone knows of