symbols

问题 I have been looking the past days how to understand Symbols in Ruby. I read every article on Google about Ruby symbols, most of them are bad explanations so I come here, and I see some questions about this topic exists, however I do not understand, sorry. From what I have read I understand that symbols are immutable and unique, so the memory consumption and performance is better than regular strings. Question #1 Are symbols purpose in life to serve the same niche as strings? Is the purpose of

问题 I'm new to the Ruby and Ruby on Rails world. I've read some guides, but i've some trouble with the following syntax. I think that the usage of :condition syntax is used in Ruby to define a class attribute with some kind of accessor, like: class Sample attr_accessor :condition end that implicitly declares the getter and setter for the "condition" property. While i was looking at some Rails sample code, i found the following examples that i don't fully understand. For example: @post = Post.find

问题 There is a .toString() on Symbol in ES6 which returns the string representation of Symbol , but wondering why '' + Symbol() doesn't work (run this expression throws out TypeError which I don't expect)? Is the latter just calling .toString() on a new Symbol and append ( + ) it to empty string? 回答1: Is the latter just calling .toString() on a new Symbol and append ( + ) it to empty string? No actually, Symbols cannot be implicitly cast to strings, or numbers, although interestingly enough you

问题 why should I use & instead of & when writing HTML for my site? Where can I find a list of other symbols that I should be encoding? (the bar / too, right?) What problems could I have if I paste the symbol right as it is into the html? The thing is , I have a few affiliate links and I'm worried that, if I write them with the & in some cases, for some reasons, because of the specific browser or device... that the info in the url wouldn't be passed correctly. Hopefully someone can clear my mind?

问题 I'm trying to define an object with a symbol as key-type since MDN says: A symbol value may be used as an identifier for object properties [...] But using it as type for the key-property: type obj = { [key: symbol | string]: string } results in the following error: TS1023: An index signature parameter type must be either 'string' or 'number'. even it can be used as index-type. I'm using the latest typescript version ( v3.7.2 ), related questions I've found: Typescript: destructuring an object

问题 I'm trying to define an object with a symbol as key-type since MDN says: A symbol value may be used as an identifier for object properties [...] But using it as type for the key-property: type obj = { [key: symbol | string]: string } results in the following error: TS1023: An index signature parameter type must be either 'string' or 'number'. even it can be used as index-type. I'm using the latest typescript version ( v3.7.2 ), related questions I've found: Typescript: destructuring an object

问题 On Linux with the GNU toolchain, I know how to control exported symbols from a shared library with a version script (gcc -Wl,--version-script=symbols.map), but I would like to list exported symbols on the command line instead. IOW, I would like the equivalent of link /EXPORT:foo from the MS toolchain. Is it possible ? EDIT: My question may not be very clearn: if I have a library libfoo.so, and I want to only export libraries foo1 and foo2, I can go create a version script foo.linux as follows

问题 I'm trying to create a Gecko 2.0-compatible DLL in Delphi. Previously (pre-Gecko 2.0) the DLL needed to export a NSGetModule() function. This worked flawlessly. Starting with Firefox 4, my DLL is getting loaded (I have verified this though a breakpoint in my initialization section), but my NSGetModule() function does not get called anymore. This is the designed behavior because starting with Gecko 2.0 (Firefox 4), a binary component is not supposed to export a NSGetModule() function: https:/

问题 I need to iterate through an object that has Symbols for keys. The following code returns an empty array. const FOO = Symbol('foo'); const BAR = Symbol('bar'); const obj = { [FOO]: 'foo', [BAR]: 'bar', } Object.values(obj) How can I iterate the values in obj so that I get ['foo', 'bar'] ? 回答1: Object.values only gets the values of all enumerable named (string-keys) properties. You need to use Object.getOwnPropertySymbols: console.log(Object.getOwnPropertySymbols(obj).map(s => obj[s])) 回答2:

问题 (Rookie mistake, I'm sure.) I'm a first year computer science student, and attempting to write a program for an assignment, with the code; import java.util.Scanner; public class Lab10Ex1 { public static void main(String[] arg) { Scanner keyboard = new Scanner(System.in); System.out.println("Please type a number: "); int n = keyboard.nextInt(); calcNumFactors(); } public static void calcNumFactors(){ System.out.print(n + 1); } } But upon compiling, I get the error; Lab10Ex1.java:10: error: