closures

问题 Does it create a new thread and then execute that anonymous function inside the new thread? I noticed many ownership / borrowing restrictions when I'm working with a closure. For example, if I have Fn() , I cannot pass a mutable variable inside the closure or it needs to be wrapped with a Mutex: fn helloworld(f: &Fn(f64)) { f(42f64); } pub fn main() { let mut killer = 2; helloworld(&|n| { println!("{}", n); killer += 1; }); } If a closure can be unsafe like that then something asynchronous or

问题 I would like to know how to create a Closure object at run-time from within a Java application, where the content of the Closure is not known ahead of time. I have found a solution but I doubt that it is optimal. Background: I have written some Groovy code that parses a Domain Specific Language. The parsing code is statically compiled and included in a Java application. In the parser implementation I have classes acting as delegates for specific sections of the DSL. These classes are invoked

问题 When compiling the following code: fn main() { let mut fields = Vec::new(); let pusher = &mut |a: &str| { fields.push(a); }; } The compiler gives me the following error: error: borrowed data cannot be stored outside of its closure --> src/main.rs:4:21 | 3 | let pusher = &mut |a: &str| { | ------ --------- ...because it cannot outlive this closure | | | borrowed data cannot be stored into here... 4 | fields.push(a); | ^ cannot be stored outside of its closure What does this error mean, and how

问题 function validateHistoryId(input) { $.getJSON('request.php', {"action": "historyExists", "history_id" : input.value}, function(data) { console.log(input.value); } ); } i use jQuery ajax call from javascript function. I tried the above code and it works, but I don't know will it cause any problems in the future. I want to know, can ajax callback function see variables of it's parent function? and is it a bad practice to do so? 回答1: This is the JavaScript functional way to doing things. It's

问题 Can anyone explain why the following produces 1,2 and the other produces 5? Should they not both produce 5? //produces 1,2 (function () { var a = [5]; function bar() { if (!a) { var a = [1, 2]; } console.log(a.join()); } bar(); })(); Based on reading some articles about JS closure, I expect them both to produce 5. Can't seem to find an article anywhere that would give some insight as to why the first block produces otherwise. //produces 5 (function () { var a = [5]; function bar() { if (a) {

问题 In my unit test I have the following code that checks whether thrown error is of expected type. It is done with two identical statements one of which doesn't compile: enum Error: ErrorType { case SomeExpectedError case SomeUnexpectedError } func functionThatThrows() throws { throw Error.SomeExpectedError } // 1) this compiles fine XCTAssertThrowsError(try functionThatThrows()) { (error) in switch error { case Error.SomeExpectedError: break //everything is fine case Error.SomeUnexpectedError:

问题 Can non-anonymous functions in PHP using 'use' keyword? Or it is available for anonymous functions only. Can I write a php file like this // L.php // assume $_texts is in this context.. $_language = null; function L_init($language) use (&$_language) { $_language = $language; } function L($key) use ($_texts, $_language) { $_texts[$_language][$key]; } So, another file can use it like this // client.php require_once 'L.php'; L_init('en'); echo L('GREETING'); // Will output localize string of key

问题 I started reading the Rust guide on closures. From the guide: That is because in Rust each closure has its own unique type. So, not only do closures with different signatures have different types, but different closures with the same signature have different types, as well. Is there a way to explicitly write the type signature of a closure? Is there any compiler flag that expands the type of inferred closure? 回答1: No. The real type of a closure is only known to the compiler, and it's not

问题 So the problem I'm having is I have a function which uses a variable in a closure and when testing it it returns a reference to the variable in it's scope. My code looks similar to the following: var app = function() { var theString = ""; //Appends ztvars onto the url passed into the function var appendString = function(url) { if (theString.length === 0) { return url; } return url+theString; }; //Used for testing, returns the function appendPageVars this.returnFunctions = function() { return

问题 Let's say we have a groovy class with some methods (static or not static). What i want to do is executing some code before and after every method of this class is invoked without touchung the class at all and without dynamically manipulating the code inside of each method. What i tried using groovy metaClass; getting all methods of the metaClass and then dynamically replacing the every method with a wrapping method, containing some code and in the middle invoking the old method. Problem is, i