protocols

问题 about websocket protocal ,you can read the detail from here,http://tools.ietf.org/html/rfc6455#section-5.3 in the mask section ,it said: The masking key is a 32-bit value chosen at random by the client. When preparing a masked frame, the client MUST pick a fresh masking key from the set of allowed 32-bit values. The masking key needs to be unpredictable; thus, the masking key MUST be derived from a strong source of entropy, and the masking key for a given frame MUST NOT make it simple for a

问题 How do I make a structure conform to protocol "Equatable"? I'm using Xcode 7.3.1 struct MyStruct { var id: Int var value: String init(id: Int, value: String) { self.id = id self.value = value } var description: String { return "blablabla" } } When I use "MyStruct", Xcode shows the error: MyStruct does not conform to protocol "Equatable" Do you have an idea to make MyStruct conform to protocol? 回答1: Swift 4.1 (and above) Updated answer: Starting from Swift 4.1, all you have to is to conform to

问题 I'd like to specify an Objective-C protocol with an optional routine. When the routine is not implemented by a class conforming to the protocol I'd like to use a default implementation in its place. Is there a place in the protocol itself where I can define this default implementation? If not, what is the best practice to reduce copying and pasting this default implementation all over the place? 回答1: Objective-C protocols have no affordance for default implementations. They are purely

问题 The following fails as per the error message quoted in the comment. It has been boiled down to the bare minimum, so the code below has no apparent practical value. I'm just trying to get a handle on the truly bizarre (in my opinion) error message. The reason I want to declare the array as [P] and not [S] is for the usual run-time polymorphism of the array contents. protocol P { func sp() } struct S: P { func sp() {} } extension Array where Element: P { func am() {} } func t() { let goodA = [S

问题 What are the size limits on DNS responses? For instance how many 'A' resource records can be present in a single DNS response? The DNS response should still be cache-able. 回答1: The largest guaranteed supported DNS message size is 512 bytes. Of those, 12 are used up by the header (see §4.1.1 of RFC 1035). The Question Section appears next, but is of variable length - specifically it'll be: the domain name (in wire format) two bytes each for QTYPE and QCLASS Hence the longer your domain name is

问题 I didn't see about it anything in Real Time Streaming Protocol (RTSP) , but when I sniffing , I saw the max rtsp packet size is 1440. And like you can see here RTSP - RTP over TCP RTP Data After the setup, RTP data will be sent through the TCP socket that is used for RTSP commands. The RTP data will be encapsulate in the following format | magic number | channel number | embedded data length | data | magic number - 1 byte value of hex 0x24 channel number - 1 byte value to denote the channel

问题 Why we need to invert crc? In which cases we need to do this? (invert mean crc = ~crc ) Is it defence from zero cases (when whole message is consists of zeros)? How it helps in this case? 回答1: You mean invert, or take the one's complement. (Reverse would mean swapping the order of the bits, undoing a CRC calculation, or reverse-engineering the CRC parameters.) That is done when the CRC parameters are defined that way. See this list of CRCs, where those with xorout defined as all 1's are

问题 Currently I'm setting the listStyle with the .listStyle(InsetGroupedListStyle()) modifier. struct ContentView: View { var body: some View { ListView() } } struct ListView: View { let data = ["One", "Two", "Three", "Four", "Five", "Six"] var body: some View { List { ForEach(data, id: \.self) { word in Text(word) } } .listStyle(InsetGroupedListStyle()) } } I want to make a property inside ListView to store the ListStyle . The problem is that ListStyle is a protocol, and I get: Protocol

问题 Currently I'm setting the listStyle with the .listStyle(InsetGroupedListStyle()) modifier. struct ContentView: View { var body: some View { ListView() } } struct ListView: View { let data = ["One", "Two", "Three", "Four", "Five", "Six"] var body: some View { List { ForEach(data, id: \.self) { word in Text(word) } } .listStyle(InsetGroupedListStyle()) } } I want to make a property inside ListView to store the ListStyle . The problem is that ListStyle is a protocol, and I get: Protocol

问题 Is there a way to have an array (or any generic type really) of generics with a type parameter conforming to a protocol? protocol MyProtocol {} struct MyStruct<T: MyProtocol> { let myProp: T } // Generic parameter 'T' could not be inferred // Explicitly specify the generic arguments to fix this issue let array1 = [MyStruct]() // Value of protocol type 'MyProtocol' cannot conform to 'MyProtocol'; // only struct/enum/class types can conform to protocols let array2 = [MyStruct<MyProtocol>]() //