• <div><p>Segmented and parallel transfers would benefit a lot from a more flexible mechanism of closures. For example these don't work: <pre><code> set ...
• Closures are functions that have access to variables from another function's scope. This is often accomplished by creating a function inside a function: function createComparisonFunction(propertyName
Closures are functions that have access to variables from another function's scope. This is often accomplished by creating a function inside a function:
function createComparisonFunction(propertyName) {
return function (obj1,obj2) {
var value1=obj1[propertyName];
var value2=obj2[propertyName];
if(value1<value2){
return -1;
}else if(value1>value2){
return 1;
}else {
return 0;
}
}
}
The highlighted lines in this example are part of the inner function ( an anonymous function) that is accessing variable ( propertyName ) from the outer function. Even after the inner function has been returned and is being used elsewhere, it has access to
that variable. This occurs because the inner function's scope chain includes the scope of createComparisonFunction().

The details of how scope chains are created and used are important for a good understanding of closures. When a function is called, an execution context is created , and its scope chain is created. The activation object for the function is initialized with
values for arguments and any named arguments. The outer function's activation object is the second object in the scope chain. This process continues for all containing functions until the scope chain terminates with the global execution context.

Whenever a variable is accessed inside a function, the scope chain is search for a variable with the given name. Once the function has completed, the local activation object is destroyed, leaving only the global scope in memory. Closures , however , behave
differently.

A function that is defined inside another function adds the containing  function's activation object into its scope chain.
let compare=createComparisonFunction("name");
let result=compare({name:"ni"},{name:"gre"});
When the anonymous function is returned from createComparisonFunction(), its scope chain has been initialized to contain the activation object from createComparisonFunction() and the global variable object. This gives the anonymous function access to all of
the variable from createComparisonFunction(). Another interesting side effect is that the activation object from createComparisonFunction() can not be destroyed once the function finishes executing , because a reference still exist in the anonymous function's
scope chain.
//create function
let compare=createComparisonFunction("name");
//call functon
let result=compare({name:"ni"},{name:"gre"});
//dereference function - memory can now be reclaimed
compare=null;
展开全文
• <p>This is a placeholder issue for implementing closures as described in https://github.com/stan-dev/design-docs/blob/master/designs/0004-closures-fun-types.md</p> <p>I say placeholder cause that'...
• <div><p>This RFC adds the ability to define generic closures: <pre><code> rust <t: debug>|x: T| println!("{:?}", x); </t:></code></pre> <p><a href=...
• <div><p>A relatively complete description of by reference closures that aims to encompass entirety of current thinking, except for bound lifetimes. <p>cc </p><p>该提问来源于开源项目：rust-lang/...
• <p>But as a first step, we should make is easy and obvious for users to tag road closures. Road closures significantly impact the navigability of OpenStreetMap. <p>Waze does a really good job of ...
• <div><p>Code like https://github.com/cornell-brg/pymtl/compare/jng55-closures?expand=1#diff-ae2a0fffb8117a39395422133340c31fL29 now works!</p><p>该提问来源于开源项目：cornell-brg/pymtl</p></...
• Mastering Ruby Closures_ A Guid - Benjamin Tan Wei Hao
• So how do I go about mapping swift closures in my plugins? <p>So like you can see here: https://auth0.com/docs/libraries/lock-ios/v2/configuration#configuring-lock-s-behavior ".withOptions" ...
• m trying to use nested closures but seem it not supported yet?, the compiler firing the following error, <p>"Zephir\CompilerException: Internal extension compilation failed. Check compile-errors....
• 326322">closures to solve this issue</a>: <pre><code>php return [ 'name' => \$faker->name, 'country_id' => function () { return factory(Country::class)->create()-...
• <div><p>Closures can be translated into some kind of struct with function pointers</p><p>该提问来源于开源项目：andrei-markeev/ts2c</p></div>
• <div><p>Zephir implemented support for closures. So now they can be used like in php instead of using separate pseudo-classes. http://blog.zephir-lang.com</p><p>该提问来源于开源项目：fezfez/...
• <div><p>Closures right now are fundamentally broken: <pre><code> fn main(){ make_window(); gtk::main(); } fn make_window(){ let mut window = gtk::Window::new(gtk::window_type::TopLevel)....
• <p>Oh god, the rules for parsing closures are even more messed up than I thought - whether or not there is an inner block or depends not only on if there are braces, but also if there is a return type...
• m wondering what kind of neat magic could be done by combining <a href="http://www.vancelucas.com/blog/practical-uses-for-php-5-3-closures/">PHP 5.3 Closures with your RainTPL templating</a>. ...
• Java ClosuresIn this article, I will explain what a closure is and clear the confusion surrounding anonymous inner classes and closures, then java’s current situation with respect to closures....
Java Closures

In this article, I will explain what a closure is and clear the confusion surrounding anonymous inner classes and closures, then java’s current situation with respect to closures.
First I want to emphasize the below two points:

As of JDK 1.6 we don’t have closures in java.
Annonymous inner classes in java are not closures.


Definition of closure

Function types and inline function-valued expression are called closures. Let me decrypt this definition for you. An anonymous function that contains some context surrounding it as a snapshot and can be passed as a parameter. This closure defintion has two parts. First one is about callback. That is, a pointer to a function that can be passed as a parameter. Second part of the definition is, this callback function will enclose some contextual information surrounding it as a snapshot and passed along with the function.

A closure is also referred to as a ‘first class object’ which can refer to attributes from its enclosing scope. As defined by Christopher Strachey in ‘Understanding Programming Languages’, a first class object can be stored in a data structure, passed as a parameter, can be returned from a function, can be constructed at runtime and independent of any identity.

In case if you are curious in Mathematics a closure is, when you operate on a members fo a set and if the resultant is always a member of that set then its called a closure.

Anonymous inner class is not closure

Anonymous classes in java are close to being called as a closure. They don’t 100% support the definition but come close to it and thats why we see lot of literature calling anonymous inner classes as closure. Why do I say its not 100%? An anonymous inner class can access “only” the final local variable of the enclosing method. It is because of this restriction, anonymous inner class in java is not a closure.

If you remember the memory management in java, you can recall that the local variables are stored in a stack. These java stacks are created when the method starts and destroyed when it returns. Unlike local variables, final fields are stored in method area which lives longer even after the return of the method. If we want to make anonymous inner class as a closure, then we should allow it to access all the fields surrounding it. But, as per the current memory management, they will be destroyed and will not be accessible after the method has returned.
Closure in Java

In that case will we get closure in java in future? We have a specification written by Peter Ahe, James Gosling, Neal Gafter and Gilad Bracha on closures for java. It gives detailed description of how a closure can be implemented in java and example code on how to use them. We have JSR 335 for closures in java named as Lambda Expressions for the Java Programming Language.

This Core Java tutorial was added on 12/05/2011.


> [from http://javapapers.com/core-java/java-closures/](http://javapapers.com/core-java/java-closures/)

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• <ul><li>Removes robot singleton</li><li>Removes command queue closures, api calls are direct calls to driver</li><li>Removes upload to Jupyter feature (since commands are no longer stored and cannot ...
• SwiftUI 内功教程之Closures 11 Escaping Closures及经典用法 什么是闭包 闭包是独立的功能块，可以在代码中传递和使用。Swift中的闭包类似于C和Objective-C中的块以及其他编程语言中的lambda。闭包可以从定义它们的...
SwiftUI 内功教程之Closures 11 Escaping Closures及经典用法
什么是闭包
闭包是独立的功能块，可以在代码中传递和使用。Swift中的闭包类似于C和Objective-C中的块以及其他编程语言中的lambda。闭包可以从定义它们的上下文中捕获和存储对任何常量和变量的引用。这称为关闭这些常量和变量。Swift为您处理捕获的所有内存管理.

Escaping Closures

Closures 可以捕获self
Escaping Closures不可以

当闭包作为函数的参数传递给闭包时，闭包被认为是对函数的转义，但是在函数返回后被调用。声明将闭包作为其参数之一的函数时，可以@escaping在参数的类型之前编写以指示允许对闭包进行转义。
闭包可以逃脱的一种方法是将其存储在函数外部定义的变量中。例如，许多启动异步操作的函数都将闭包参数用作完成处理程序。该函数在开始操作后返回，但是直到操作完成后才调用闭包-该闭包需要转义，稍后再调用。例如：
var completionHandlers = () -> Void
func someFunctionWithEscapingClosure(completionHandler: @escaping () -> Void) {
completionHandlers.append(completionHandler)
}
该someFunctionWithEscapingClosure(_:)函数将闭包作为其参数，并将其添加到在函数外部声明的数组中。如果未使用标记该函数的参数@escaping，则会出现编译时错误。
self如果self引用的逃逸闭包是引用类的实例，则需要特别考虑。self用逃逸的闭包进行捕获可以轻松地意外创建一个强大的参考周期。有关参考循环的信息，请参见自动参考计数。
通常，闭包通过在闭包主体中使用变量来隐式捕获变量，但是在这种情况下，您需要明确表示。如果要捕获self，请self在使用时明确编写，或包括self在闭包的捕获列表中。self明确写作可以表达您的意图，并提醒您确认没有参考周期。例如，在下面的代码中，传递给的闭包显式地someFunctionWithEscapingClosure(:)引用self。相比之下，传递给的闭包someFunctionWithNonescapingClosure(:)是一个不冒漏的闭包，这意味着它可以self隐式引用。
func someFunctionWithNonescapingClosure(closure: () -> Void) {
closure()
}

class SomeClass {
var x = 10
func doSomething() {
someFunctionWithEscapingClosure { self.x = 100 }
someFunctionWithNonescapingClosure { x = 200 }
}
}

let instance = SomeClass()
instance.doSomething()
print(instance.x)
// Prints "200"

completionHandlers.first?()
print(instance.x)
// Prints "100"

这doSomething()是捕获的一个版本，将self其包含在闭包的捕获列表中，然后self隐式引用：
class SomeOtherClass {
var x = 10
func doSomething() {
someFunctionWithEscapingClosure { [self] in x = 100 }
someFunctionWithNonescapingClosure { x = 200 }
}
}


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• They could probably be implemented, but then you guys would have to make a decision on how they should work with closures. <p>I've tested this with a closure throwing a 404 exception, returning ...

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